Extended Incident Handling Working Group Kathleen M. Moriarty draft-ietf-inch-rid-00.txt MIT Lincoln Laboratory Expires: August 28, 2004 February 28, 2004 Incident Handling: Real-Time Inter-Network Defense Status of this Memo This document is an Internet-Draft and is subject to all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract Network security incidents such as Denial of Service (DoS), system compromises, worms, and viruses typically result in the loss of service, data, and resources both human and system. Security incidents can be detrimental to the health of the network as a whole. Network Providers (NP) need to be equipped and ready to assist in tracing security incidents with tools and procedures in place before the occurrence of an attack. This paper proposes a proactive inter-network communication method to integrate existing tracing mechanisms across NP boundaries to identify the source(s) of an attack. The various methods implemented to detect and trace attacks must be coordinated on the NPs network as well as provide a communication mechanism across network borders. It is imperative that NPs have quick communication methods defined to enable neighboring NPs to assist in tracking a security incident across the Internet. This proposal integrates current incident detection and tracing practices for network traffic, which could be extended for security incident handling. Policy guidelines for handling incidents are recommended and can be agreed upon by a consortium using the defined protocol and extended to each NP's clients. Internet-Draft February 28, 2004 TABLE OF CONTENTS Status of this Memo ................................................ 1 Abstract ........................................................... 1 1. Introduction .................................................... 4 1.1 Overview of Attack Types ................................... 5 2. Recommended Network Provider (NP) Technologies .................. 7 3. Characteristics of Attacks ...................................... 8 3.1 Tracing a Distributed attack ............................... 10 3.1.1 Tracing Security Incidents ........................... 10 3.2 Trace Approaches ........................................... 11 3.2.1 Trace approach via Traffic Flow Analysis ............. 11 3.2.2 Trace Approach via Hash-Based IP Traceback ........... 12 3.2.3 IP Marking ........................................... 13 3.3 Correlating Collected Data ................................. 14 4. Communication Between Network Providers ......................... 14 4.1 Inter-Network Provider RID Messaging ....................... 16 4. RID Network Topology ............................................ 18 4.2 Message Formats ............................................ 19 4.2.1 RID Messages using SOAP and Web Services Security Model 20 4.2.2 RID Data Types ....................................... 20 4.2.4 IODEF-Document ...................................... 21 4.2.5 IODEF-Document Extensions ............................ 21 4.2.5.2 NPPath Extension ............................... 25 4.2.5.3 TraceStatus Extension ......................... 26 4.3 RID Documents Defined by Message Type Derived from IODEF ... 27 4.3.1 Trace Request ........................................ 29 4.3.2 Trace Authorization Message .......................... 30 4.3.3 Source Found Message ................................. 31 4.3.4 Relay Message Request ................................ 32 4.3.5 Example Upstream Trace ............................... 34 4.3.6 RID Trace Request Example ............................ 35 5. RID IODEF Extension Document Type Definition .................... 37 6. Message Transport ............................................... 40 6.1 Message Delivery Protocol - Integrity and Authentication ... 40 6.2 Transport Communication .................................... 41 6.3 Authentication of RID Protocol ............................. 41 6.4 Authentication Considerations for a Multi-hop Trace Request 42 6.4.1 Public Key Infrastructures and Consortiums ........... 43 6.5 Privacy Concerns and System Use Guidelines ................. 44 7. Security Considerations ......................................... 47 Moriarty Expires: August 28, 2004 [Page 2]
Internet-Draft February 28, 2004 8. Summary ......................................................... 49 9. References ...................................................... 50 9.1 Acknowledgements ........................................... 53 9.2 Author Information ......................................... 53 Moriarty Expires: August 28, 2004 [Page 3]
Internet-Draft February 28, 2004 1. Introduction Incident handling involves the identification of the source of an attack, whether it be a system compromise or a denial of service attack. In order to identify the source of an attack, there must be a way to trace the attack traffic iteratively upstream through the network to the source. In cases where an active session between the compromised system and the attacker or source system is available, the source is easy to identify as in the case of attacks where the source address was not spoofed and sufficient evidence is left behind. The problem of tracing incidents becomes more difficult when the source is obscured or spoofed, logs are deleted, and the number of sources are overwhelming. Current approaches to mitigating the effects of security incidents, DoS, and DDoS attacks are aimed at identifying and filtering or rate limiting packets from attackers who seek to hide the origin of their attack by source address spoofing from multiple locations. Measures can be taken at network provider (NP) border routers providing ingress, egress, and broadcast filtering as a recommended best practice in RFC2827. These filters ensure that traffic leaving and entering client locations contains valid source and destination addresses. Network providers have devised solutions to trace attacks across their backbone infrastructure to either identify the source on their network or the next upstream network in the path to the source. Many of the single network tracing mechanisms have been developed as in-house solutions and are specific to the network that is traced. Techniques such as collecting packets as traffic traverses the network have been implemented to provide the capability to trace attack traffic after an incident has occurred. Other methods use flow based traffic analysis to trace traffic across the network in real time or packet marking techniques. The single network trace mechanisms use similar information across the individual networks to trace traffic. Problems are encountered when an attempt is made to have a trace continued through the next upstream network since the trace mechanism and management may be different. In the case where the traffic traverses multiple networks, there is currently no established communication mechanism to provide the ability to continue the trace. If the next upstream network has been identified, a phone call might be placed to contact the network administrators in hopes to have them continue the trace. A communication mechanism is needed to facilitate the transfer of information needed in order to continue traces accurately and efficiently to upstream networks. The communication mechanism described in this paper, Real-time Inter-network Defense (RID), takes into consideration the information needed by various single network trace implementations and the needs of network providers to have the ability to decide if a trace request should be permitted Moriarty Expires: August 28, 2004 [Page 4]
Internet-Draft February 28, 2004 to continue. The data in RID messages will be represented in an Extensible Markup Language (XML) document and is an extension of the Incident Data Exchange Format (IODEF) model. By following this model, integration with other aspects of the network for incident handling is simplified. Finally, methods are incorporated into the communication system to indicate what actions were taken closest to the source in order to cease or mitigate the effects of the attack at hand. RID is intended to provide a method to communicate the relevant information between NPs while being compatible with a variety of existing and possible future detection and tracing approaches. Security and privacy considerations are of high concern since potentially sensitive information may be passed through RID messages. RID messaging will take advantage of XML security, web services security model, and will wrap RID messages in the Simple Object Access Protocol (SOAP) to use the authentication, integrity, and authorization features each has to offer to achieve the level of security that is necessary. SOAP and WS-Security provide the necessary security for a protool like RID, but may cost too much in terms of overhead. BEEP, XML SNMP, and other transport methods are also under consideration. 1.1 Overview of Attack Types The CERT Coordination Center published a paper in October, 2001 entitled, "Trends in Denial of Service Attack Technology"[6]. The paper outlined the behavior of Denial of Service attacks of both single-source and multiple-source origins. Denial of Service (DoS) attacks attempt to consume bandwidth, processing power, or system resources for the purposes of denying use by normal users. Bandwidth-based attacks flood systems with TCP, UDP or ICMP packets. Bandwidth or processing power based attacks may use variations on these packets, such as altering the source address, port numbers, or TCP options. Many attacks types including various DoS attacks and system compromise use tactics such as altering port numbers to enable packets to bypass packet filters. Other approaches are to use packets, which are targeting valid services hosted by the network since they must be permitted and the attack traffic cannot be deciphered from valid network traffic. In bandwidth based DoS attacks, tactics including altering the source address as in the case of an ICMP attack where packets are sent through a site with the IP direct broadcast option enabled on the site's router. The IP directed broadcast would amplify the number of packets sent to the victim, thus flooding the network and consuming bandwidth. Another type of DoS attack is aimed at consuming system resources, as in the SYN flood attack. A SYN flood attack is a TCP attack where the initiator of the attack begins the TCP handshake sequence Moriarty Expires: August 28, 2004 [Page 5]
Internet-Draft February 28, 2004 by sending a SYN packet to the destination server of the attack with a spoofed source address. The server responds with an acknowledgement of the SYN packet, but the response packet is sent to the spoofed source address, which does not accept the unexpected acknowledgment packet. This leaves the connection open on the server and consumes system resources. There are a limited number of connections a server can maintain, and once this limit is reached, valid connections are denied. This is just one example of a class of attacks targeting a single system or service to prevent valid traffic from accessing the system. DoS attacks are characterized by large amounts of traffic destined for particular Internet locations and can originate from a single or multiple sources. An attack from multiple sources is known as a Distributed Denial of Service attack (DDoS). Because DDoS attacks can originate from multiple sources, tracing such an attack can be extremely difficult or nearly impossible. These attacks can be launched from systems across the Internet unified in their efforts or by compromised systems enlisted as 'zombies' that are controlled by servers, thereby providing anonymity to the controlling server of the attack. DDoS attacks do not necessarily spoof the source of an attack since there are a large number of source addresses, which make it difficult to trace anyway. DDoS attacks can also originate from a single system or a subset of systems that spoof the source address in packet headers in order to mask the identity of the attack source. Compromising a system can be accomplished through one of many attack vectors, using various techniques from a remote host or through a local privilege escalation attempts. The attack may exploit a system or application level vulnerability that may be the result of a design flaw or a configuration issue. A compromised system, as described above, can be used to later attack other systems. The subsequent attacks may be targeted systems or an attempt to recruit zombies to later be used in DoS or DDoS attacks. Identifying the sources of system compromises may also be difficult since an attacker may access the compromised system from various sources. The attacker may also take measures to hide their tracks by deleting log files or by accessing the system through a series of compromised hosts. System compromises may occur from valid source addresses, which may also be the case for other security incidents such as worms, Trojans, or viruses. It is often the case that an incident goes unreported even if valid source address information is available. Incident handling is a difficult task for a NP and even at some client locations due to the size of a network and resource limitations. Moriarty Expires: August 28, 2004 [Page 6]
Internet-Draft February 28, 2004 2. Recommended Network Provider (NP) Technologies For the purpose of this document, a network provider (NP) shall be defined as a backbone infrastructure manager of a network or the network provider's Computer Security Incident Response Team (CSIRT). The backbone may be that of an organization providing network (Internet or private) access to commercial, personal, government, and educational institutions or the backbone provider of the connected network. The connected network provider is an extension meant to include Intranet and Extranet providers as well as instances such as a business or educational institute's, (etc.) private network. NPs typically manage and monitor their networks through a centralized network management system (NMS). The acronym NMS will be used to generically represent management servers on a network used for the management of network resources and the integration of RID messaging with other components of the network. This system usually performs trend analysis for bandwidth utilization and report communication problems and in this case may also trigger a trace across the network or communicate with a system that can initiate a trace. As a part of the bandwidth trend analysis performed, denial of service traffic or unusually unexpected increases in bandwidth could also be reported. With the capability of seeing the entire network under management, the NMS could be utilized to trace to the origin of network traffic within its own network. NPs could become proactive in handling denial of service attacks through the use of tools already in existence on their networks. If trend analysis is not already being performed for bandwidth utilization, this may require the use of an additional server to perform this function. Such a server would need to account for traffic redirection events resulting in bandwidth fluctuations due to networking problems in other areas of an NP's backbone. Ideally, this system would have the ability to perform a trend analysis on the network to determine if there was an unusually large increase in traffic without explanation, such as a network event elsewhere on the backbone. Client events, such as the launch of a new web site or streaming video of a noteworthy news event should be programmable exceptions to the alert. Once it can be determined that the event may be significant, a trace back for the source of the increased traffic should be performed through analysis on the neighboring connections on the network. If possible, the trace may need to inspect packets to determine a pattern, which could assist reverse path identification. This may be accomplished by inspecting packet header information such as the source and destination IP addresses, ports, and protocol flags to determine if there is a way to distinguish them from other packets. A description of the incident along with any available automated trace data should trigger an alert to the NPs security team for further investigation. The proactive monitoring for bandwidth related attacks could use Moriarty Expires: August 28, 2004 [Page 7]
Internet-Draft February 28, 2004 trending analysis as a guideline to determine acceptable levels of traffic across the network. Unexplained and extended spikes in traffic would be a signal that a DoS attack may be in progress. Resource related attacks would be more difficult to detect because the effects of resource exhaustion are not readily apparent in network traffic. Methods such as trending the packet size of traffic to and from networks may be an indicator of this type of attack. For example, if there is a large increase in small packets sent to and from a network, that may be an indicator of a SYN flood attack. TCP connections begin with small packets, but the session data over the established connection may be a mixture of large and small packets. A change in the size of packets to or from a network or host may be an indicator of a DoS attack using different types of traffic than normally seen in the monitored network. Intrusion detection system (IDS) may also be integrated to create IODEF documents or RID messages to facilitate security incident handling. IDS monitor network traffic analyzing packets to determine if traffic might be classified as malicious. If an IDS detects malicious traffic, an analyst might determine the validity and severity of the attack traffic and determine if a trace is necessary. If the analyst determines a trace should be initiated, an IODEF document with RID extensions might be created or the necessary information sent to the RID messing system in order to create and track the RID message. The detection of other security incidents may rely more on reporting rather than automated detection tools, except perhaps in the case of some worms, which can result in large increases of traffic. Detection of a security incident is outside the scope of this paper, however it should be possible to integrate detection methods with RID messaging. 3. Characteristics of Attacks The goal of tracing a security incident may be to identify the source or to find a point on the network as close to the origin of the incident as possible. A security incident may be defined as a system compromise, a worm or Trojan infection, or a single or multiple source denial of service attack. Incident tracing can be used to identify the source(s) of an attack in order to cease or mitigate the undesired behavior. The communication system, RID, described in this paper can be used to trace any type of security incident and allows for actions to be taken when the source of the attack or a point closer to the source has been identified. The purpose of tracing an attack would be to cease or mitigate the affects of the attack through methods such as filtering or rate limiting the traffic close to the source or by using methods such as taking the host or network offline. Care must also be taken to ensure the system is not abused and to use proper analysis in determining if attack traffic is in fact attack traffic at each NP along the path of a trace. Moriarty Expires: August 28, 2004 [Page 8]
Internet-Draft February 28, 2004 Tracing security incidents can be a difficult task since attackers go to great lengths to obscure their identity. In the case of a security incident, the true source might be identified due to an existing established connection to the attackers point of origin. However, the attacker may not connect to the compromised system for a long period of time after the initial compromise or may access the system through a series of compromised hosts spread across the network. Other methods of obscuring the source may include targeting the host with the same attack from multiple sources using both valid and spoofed source addresses. This tactic can be used to compromise a machine and leave a difficult task of locating the true origin for the administrators. DDoS attacks are also difficult or nearly impossible to trace because of the nature of the attack. Some of the difficulties in tracing these attacks include: O the attack originates from multiple sources, O the attack may include various types of traffic meant to consume server resources, such as a SYN flood attack without a significant increase in bandwidth utilization, O the type of traffic could include valid destination services, which cannot be blocked since they are essential services to business, such as DNS servers at an NP or HTTP requests sent to an organization connected to the Internet, O the attack may utilize varying types of packets including TCP, UDP, ICMP, or other IP protocols. O the attack may use a very small number of packets from any particular source, thus making a trace after the fact nearly impossible. If the source(s) of the attack cannot be determined from IP address information or tracing the increased bandwidth utilization, it may be possible to trace the traffic based on the type of packets seen by the client. In the case of packets with spoofed source addresses, it is no longer a trivial task to identify the source of an attack. In the case of an attack using valid source addresses, methods such as the traceroute utility can be used to fairly accurately identify the path of the traffic between the source and destination of an attack. If the true source has been identified, actions should be taken to cease or mitigate the effects of the attack by reporting the incident to the NP or the upstream NP closest to the source. In the case of spoofed source address other methods can be used to trace back to the source of an attack. The methods include packet filtering, packet hash comparisons, IP Marking techniques, ICMP Traceback, and packet flow analysis. As in the case of attack detection, tracing traffic across a single network is a function that can be used with RID in order to provide the networked ability to trace spoofed traffic to the source, while Moriarty Expires: August 28, 2004 [Page 9]
Internet-Draft February 28, 2004 RID provides all the necessary information to accommodate the approach used on any single network to accomplish this task. RID can also be used to report attack traffic close to the source where the IP address used was determined to be valid. 3.1 Tracing a Distributed attack Tracing a DDoS attack is a very difficult problem. Since DDoS attacks may involve multiple sources with spoofed addresses, there may only be a small amount of traffic from each of the originating hosts. This makes it difficult to trace back to the sources. The sources may also alternate the type of traffic and the master may vary the sources from within the pool of sources launching the attack. Because of the dynamic nature of the DDos attack, immediate action would need to be taken to have any hope of locating the origin(s) of the attack with a near real-time trace. In order to identify a DoS attack or DDoS, a client may notify its NP that it is currently under attack. Automated methods might include statistical traffic analysis, which looks for unexpected fluctuations in bandwidth or in the size and types of packets sent between networks, hosts, or an IDS. There is on-going research in the area of detecting DoS and DDoS, and any effective techniques could be integrated with the tracing techniques described in this paper. Some research approaches include methods that detect backscatter traffic [3], using a data structure for bandwidth attack detection [4], and monitoring congestion through packet retransmission information [5]. Another detection method may include monitoring any changes in the size of packets sent to and from a network. For example, if a site that normally receives small packets and replies with large packets experiences a change in traffic pattern such as the sending and receiving of large amounts of either small or large packets, this could indicate a DoS attack. Once an attack has been detected through traffic analysis and bandwidth usage statistics, traces would have to quickly identify the various sources of the attack. Once an attack is detected, a generalized approach to tracing back connections might include the inspection of packet header information such as the destination IP address and any distinguishing header values of the traffic seen by the site during the attack. 3.1.1 Tracing Security Incidents If a trace can identify the sources of a distributed attack, blocking the sources at the NP level close to the attacker could be an immediate action to stop the attack. In the case of a DDoS attack, further information may be obtained from the attacking computers as to the controller of the attack sending the 'zombies' control information to carry out the attack. A similar example of attack traffic with the possibility of multiple traces required Moriarty Expires: August 28, 2004 [Page 10]
Internet-Draft February 28, 2004 would be one in which an attacker compromised a series of systems and accomplished hiding their source by logging into a string of systems to launch the attack. This additional trace is beyond the scope of this paper, but may use additional tracing mechanisms such as sniffing the network to locate the controllers of the attack. Finding a faster and more efficient way to trace multiple sources of an attack is essential to combating DDoS attacks. The ability to quickly relay and act upon the trace information gathered is imperative to stopping attack traffic. Tracing multiple attack paths can also cause additional stress on the network and does not scale well. A CSIRT report might be generated in the form an of IODEF document and then fed into a RID message or document to facilitate a trace of attack traffic. 3.2 Trace Approaches There have been many separate research initiatives to solve the problem of tracing upstream packets to detect the true source of attack traffic. Upstream packet tracing is currently confined to the borders of a network or a NP's network. Traces require access to network equipment and resources, which limit a trace to a specific network. Once a trace reaches the boundaries of a network, the network manager or NP adjacent in the upstream trace must be contacted in order to continue the trace. NPs have been working on individual solutions to accomplish upstream tracing within their own network environment. The tracing mechanisms implemented thus far have included proprietary or custom solutions requiring specific information such as IP packet header data, hash values of the attack packets, or marked packets. Hash values are used to compare a packet against a database of packets that have passed through the network in the case of 'Hash Based IP Traceback'[8]. Other research solutions involve marking packets as explained in 'ICMP Traceback Messages'[10], 'Practical Support for IP Traceback' [9], and *** IP Marking []***. The following sections outline some available solutions for implementing traceback within the confines of a network managed by a single entity. Later in the paper the focus will be on the information needed to accomplish the trace and to make possible the Inter-NP communication specified. 3.2.1 Trace approach via Traffic Flow Analysis Traffic flow analysis is used to monitor individual network traffic streams, such as a single TCP session beginning with the SYN packet and ending with the final FIN ACK in a session. There have been a few efforts to standardize flow analysis for network management, one through the traffic flow management MIB and another through NetFlow. The 'Traffic Flow Management' RFC [RFC2720] was Designed to provide management information such as behavior models, Moriarty Expires: August 28, 2004 [Page 11]
Internet-Draft February 28, 2004 Capacity planning, network performance, quality of service, and Attribution of network usage to system administrators. NetFlow from Cisco [7] provides similar capabilities to the traffic flow mib, except that it is specific to IP traffic and has already been implemented for traffic management in Cisco equipment. Although NetFlow was developed by Cisco, it is also an open standard. The flow analysis in both implementations can monitor with a capture filter on source and destination addresses, the number of packets and the count of bytes in each flow, the originating interface of the traffic, and the upstream peer information. The upstream peer information is essential to tracing a spoofed packet back to the true origin. There are several differences in the implementations and the monitor and capture capabilities of the two flow analysis implementations. NetFlow collects all packets and maintains the following information on packet flows for later analysis: O Source and destination IP address O Source and destination TCP/User Datagram Protocol (UDP) ports O Type of service (ToS) O Packet and byte counts O Start and end timestamps O Input and output interface numbers O TCP flags and encapsulated protocol (TCP/UDP) O Routing information (next-hop address, source autonomous system (AS) number, destination AS number, source prefix mask, destination prefix mask) Based on the information listed above, a spoofed packet can be traced upstream through a network to either identify the true source or the upstream peer. Various flow based solutions have been developed and implemented for use on a single backbone based on flow analysis and the RID messaging described later must be able to support existing and future solutions to trace attacks across multiple networks. The AS number listed associated with a source IP address is only valid if the source IP address is valid. The AS number in this case cannot be trusted, however it may be trusted in the iterative trace and from the actual address information gathered from that trace. 3.2.2 Trace Approach via Hash-Based IP Traceback BBN implemented a trace back solution, which collects hashes of IP packets across the network. The Hash-Based IP Traceback was designed specifically to trace attack traffic and achieve the following objectives O trace attacks after specific flows of the attack have completed O reduce storage requirements needed to save traceable packet data O provide a secure method to store packet captures on the Internet Moriarty Expires: August 28, 2004 [Page 12]
Internet-Draft February 28, 2004 Hash-based IP traceback is another solution to provide the ability to trace attack traffic. By capturing all packets across the network and saving hash values for the IP header information that does not get altered as it traverses the network, attacks can be traced after the fact. Since hashes of IP header information are stored instead of the actual header information, privacy concerns are no longer an issue as might be the case with packet captures across the Internet. If a system used to store the packet captures was compromised, the data could not be used to identify which entities are 'talking' to each other on the Internet. BBN also considered how traces could be performed across a single network, for example an NP's backbone. The solution divides the network up into regions, each with its own collection station. The trace might be initiated at a particular collection station where data for a specific router is stored. When the collection station traces through its database for the matches of particular hashes of IP packets, it follows the trace through the network equipment for its own region. The collection station then determines which bordering region was the next upstream source of the attack and the trace is continued at the next collection agent. The trace continues until the source is identified or a neighboring network is identified as the upstream source of the attack. The upstream network must then be notified in some way in order to continue the trace. The upstream network will require the IP packet information in order to continue the trace. The upstream provider will want to look at its network and resources and decide if it would like to initiate a trace across their network. A limited number of packets can be stored based on resources and network traffic loads. A possible solution for communicating the upstream trace request between bordering networks is discussed later with the RID protocol. The trace solution implemented across the single network is independent of the messaging system and would have a greater impact on the effectiveness and efficiency of a trace across the network. 3.2.3 IP Marking IP Marking is another technique that can be used to trace attacks in which the source address has been spoofed in a more efficient manner than iterative trace mechanisms. This technique has been proposed specifically in terms of tracing DoS attacks across a network. All information is correlated at the end node or the target where the packets received would have been marked probabilistically along the path of the traffic. This method requires that routers and other infrastructure equipment have the ability to mark packets so that the path they tool can be derived at the destination address for the packets. Since all packets are not marked, depending on the IP Marking scheme used, a number of Moriarty Expires: August 28, 2004 [Page 13]
Internet-Draft February 28, 2004 similar packets would have to be sent from a single source in order for it to be identified. IP Marking alone may not be a complete answer for tracing traffic, since an attacker could switch their methods to send very little data from any one host used in a DDoS attack, thus making it unlikely that enough packets will be marked to find the source of each stream. Integrating IP Marking with other techniques may be the best answer to ensure the efficiency and robustness of the system as a whole. In terms of integrating the IP Marking approach with RID there are several ways in which it may be useful. IP Marking may be used to gather information about the path of the trace up to an including identifying the actual source. A peer closer to the source might be identified if the IP Marking technique were not able to fully reconstruct the path of the trace. In this instance, the trace information could be sent to the closest point identified in the path from the IP Marking technique, thus shortening the length of time required to trace the traffic through the network. If a source was identified, a ID Relay request might be used in order to trigger a specific action to take place close to the source to mitigate or stop the affects of the attack. 3.3 Correlating Collected Data Integrating this extended monitoring capability into the NMS would allow for the formulation of network behavior statistics and thus the detection of anomalous usage behavior. The network trend analysis capability could be used to detect unexplained spikes in bandwidth usage on the network as a whole, as well as, on specific networks in an NP backbone or servers on a local network. The NMS would be aware of network outages that may result in traffic being redirected through alternate paths of the network, which would be an example of an explained spike in bandwidth. A client connected to an NP may be hosting an event, such as a web cast. An abundance of valid connection attempts can also result in bringing a web site down, exhausting either bandwidth or system resources. If an NP was aware of such an event, it could set higher thresholds for bandwidth usage alerting during that period of time to prevent false alarms. The anomalies could be used as methods of detecting Denial of Service attacks, worms or other security incidents. IDS systems may detect attacks and redistribute information into an NMS or RID messaging system to facilitate an attack traffic trace in order to mitigate or stop the traffic. 4. Communication Between Network Providers Expediting the communication between NPs is essential when responding to a security related incident, which may cross network access points, (Internet backbones) between providers. As a result of the urgency involved in this inter-NP security incident communication, there must be an effective system in place to Moriarty Expires: August 28, 2004 [Page 14]
Internet-Draft February 28, 2004 facilitate the interaction. This communication policy or system should involve multiple means of communication to avoid a single point of failure. Email may be the best way to transfer information about the incident, packet traces, etc. However, email may not be received in a timely fashion or be acted upon with the same urgency as a phone call or other communication system. Each NP should dedicate a phone number to reach a member of their security incident response team. The phone number could be dedicated to inter-NP incident communications and must be a hotline that provides a 24x7 live response. The phone line should reach someone who would have either the authority and expertise or the means to expedite the necessary action to investigate the incident. This may be a difficult policy to establish at smaller NPs due to resource limitations, so another solution may be necessary. An outside group may be able to serve this function given the necessary access to the NPs network. The outside resource should be able to mitigate or alleviate the financial and experience resource limitations. A technical solution to trace traffic across a single NP may include home grown or commercial systems in which RID messaging must accommodate the input requirements. The network management systems used on the NPs backbone to coordinate the trace across the single network requires a method to accept and process RID messages and relay trace requests to the system as well as wait for responses from the system to continue the RID request process as appropriate. In this scenario, each NP would maintain their own RID system and integrate with a management station used for network monitoring and analysis. An alternative for NPs lacking sufficient resources may be to have a neutral third party with access to the NPs network resources that could be used to perform the trace functions. This could be a function of a central organization operating as a computer response team for the Internet as a whole or within a consortium that may be able to provide centralized resources. Consortiums would consist of a group of NPs that agree to participate in the RID communication protocol with an agreed upon communication protocol facilitating the secure transport of RID XML documents via the Simple Object Access Protocol (SOAP). The first method described prevents the need to permit access to other network's equipment through the use of a standard messaging mechanism to enable RID or NMS's to communicate trace information to other networks in a consortium or in neighboring networks. The third party mentioned above may be used in this technical solution to assist in facilitating traces through smaller NPs. The messaging mechanism may be a logical or physical out-of-band network to ensure the communication is secure and unaffected by the state of the network under attack. The two management methods would accommodate the needs of larger NPs to maintain full management of their network and the third party option could be available to smaller NPs who lack the necessary human resources to Moriarty Expires: August 28, 2004 [Page 15]
Internet-Draft February 28, 2004 perform a trace. The first method enables the individual NPs to involve their network operations staff to authorize the continuance of a trace through their network via a notification and alerting system. The out-of-band logical solution for messaging may be permanent virtual circuits configured with a small amount of bandwidth dedicated to NMS communications between NPs. The network used for the communication, out-of-band or protected channels discussed later, would be direct communication links to relay RID messages, accepting only this messaging protocol. The communication links would be direct connections between network peers who have agreed upon use and abuse policies through the use of a consortium. Consortiums might be linked through policy comparisons and additional agreements to form a larger web or iterative network of peers that correlates to the traffic paths available over the larger web of networks. The maintenance of the individual links will be the responsibility of the two network peers hosting the link. Within a consortium, a web of connections might be formed in order to facilitate fast communications for relay messages described later for the RID protocol. Contact information, IP addresses of network management systems and other information must be coordinated between by a consortium and may use existing databases, such as the Routing Arbitor, as with any changes to the involved systems. The security, configuration, and confidence rating schemes of the peering NMSs for RID messaging peers must be negotiated by peers and must meet certain overall requirements of the fully connected network, (Internet, government, education, etc.) through the peering and/or a consortium based agreement. RID messaging established with clients of an NP may be negotiated in a contract as part of a value added service or through a service level agreements. Further discussion is beyond the scope of this document and may be more appropriately handled in network peering or service level agreements. Procedures for incident handling need to be established and well known by anyone that may be involved in incident response. The procedures should also contain contact information for internal escalation procedures, as well as external assistance groups such as a CSIRT, CCCERT, GIAC, and the FBI. 4.1 Inter-Network Provider RID Messaging In order to implement a messaging mechanism between RID communication or NMS systems, a standard protocol and format is required to ensure inter-operability between vendors. The messages would have to meet several requirements in order to be meaningful as they traversed multiple networks. The Real-Time Inter-Network Defense (RID) provides the framework necessary for communication between networks involved in the trace back and mitigation of a DoS attack or security incident. There are several types of messages Moriarty Expires: August 28, 2004 [Page 16]
Internet-Draft February 28, 2004 that are needed to facilitate a trace across multiple networks. The message types include a Trace Request, Trace Authorization, Source Found, and a Relay Request. A Trace Request message can be used when the source of the traffic may have been spoofed, which may require each network provider in the upstream path to receive a trace request and issue a trace across their network in order to determine the upstream source of the traffic. The Trace Authorization and Source Found messages are used to communicate the status and result of a trace as it traverses potentially several networks. The last message type would be used to leverage the bi-lateral relationships or a consortium's interconnections to relay a request in order to mitigate or stop potentially malicious or spurious valid traffic close to the source. This request type (4), called a Relay Request, would only involve the RID communication systems along the path to the source of the traffic and not involve the use of single network trace systems. Routes would determine the fastest path to a known source IP address in the case of a relay request or type four message. A message sent between RID or NMS systems to request the continuance of a trace or to relay a request to stop traffic at the source through a bordering network would require the information enumerated below. 1. Enough information to enable the network administrators to make a decision about the importance of continuing the trace. 2. The filter or IP packet hash information needed to carry out the trace. 3. Contact information of the origin of the trace. The contact information could be provided through the autonomous system number [RFC1930] or NIC handle information listed in the Registry for Internet Numbers or other Internet databases. 4. Network path information to help prevent any routing loops through the network from perpetuating a trace. If an NMS receives a trace request containing its own information in the path, the trace must cease and the NMS should generate an alert to inform the network operations staff that a routing loop exists. 5. A unique identifier for a single attack should be used to correlate traces to multiple sources in a DDoS attack. Use of the communication network and the RID protocol must be for pre-approved, authorized purposes only. It is the responsibility of each participating party to adhere to guidelines set forth in both a global use policy for this system as well as one established though the peering agreements for each bilateral peer or agreed upon consortium guidelines. The purpose of such policies are to avoid abuse of the system and shall be developed by a consortium of participating entities. The global policy may be dependent on the domain in which it operates under, for example, a government network or a commercial network such as the Internet would adhere to different guidelines to address the individual concerns. Privacy issues must be considered in public networks such as the Internet. Privacy issues are discussed later in the Moriarty Expires: August 28, 2004 [Page 17]
Internet-Draft February 28, 2004 security section along with other requirements that must be agreed upon by participating entities. Traces must be legitimate security related incidents and not used for purposes such as sabotage or censorship. An example of such abuse of the system would include a request to rate limit legitimate traffic to prevent information from being shared between users on the Internet (restricting access to online versions of papers) or restricting access from a competitor's product in order to sabotage a business. The RID system should be configurable to either require user input or automatically continue traces. This feature would enable a network manager to assess the available resources before continuing a trace. A trace may cause adverse affects on a network. If the confidence rating is low it may not be in the Network Provider's best interest to continue the trace. The confidence ratings must adhere to the specifications for selecting the percentage used to avoid abuse of the system. Trace requests must be issued by authorized individuals from the initiating network, set forth in policy guidelines established through peering or SLA agreements. 4. RID Network Topology The most basic topology for RID systems that communicate with each other would be a direct connection or a bi-lateral relationship as illustrated below. __________ __________ | | | | | RID |__________-------------___________| RID | |_________| | NP Border | |________| ------------- Figure 1: Direct Peer Topology Within the consortium model, several topologies might be agreed upon and used. One would leverage bi-lateral network peering relationships of the members of the consortium. The peers for RID would match that of routing peers and the logical network borders would be used. This approach may be necessary for an iterative trace where the source is unknown. The model would look like the above diagram, however there may be an extensive number of inter- connections of bi-lateral relationships formed. Also within a consortium model, it may be useful to establish an integrated mesh of networks to pass RID messages. This may be beneficial where the source address is known and an interconnection may provide a faster route to reach the closest upstream peer to the source of the attack traffic. A possible example is illustrated below. Moriarty Expires: August 28, 2004 [Page 18]
Internet-Draft February 28, 2004 _______ _______ ______ | | | | | | __| RID |____-------------____| RID |____-------------____| RID |__ |_____| | NP Border | |_____| | NP Border | |_____| | ------------- ------------- | |_______________________________________________________| Direct connection to network that is not an immediate network peer Figure 2: Mesh Peer Topology By using a fully meshed model that may occur in a consortium, broadcasting RID requests would be possible, but not advisable. By broadcasting a request, RID peers that may not have had the attack traffic appear on their network would be asked to perform a trace in order to possibly speed the time in which the true source was identified. The initiating network would not have first performed a trace on their own network to identify the next upstream peer or if the source of the traffic was actually on their own network. If the source was later to be found on the same network as the initiating peer, unnecessary resources would have been utilized for this unnecessary trace request(s). 4.2 Message Formats The following section describes the four message types used to facilitate the communication between NPs tracing an incident based on the IODEF model. The messages would be generated and received on RID communication systems or NMSs on the NPs network. The messages may originate from other IODEF messages from intrusion detection servers, CSIRTS, etc.. A RID message uses the IODEF framework which is encapsulated in a SOAP wrapper to enable the parsing of the various types of RID messages and IODEF extensions for RID through the use of the AdditionalData class in the IODEF model. Each type of RID message is described in the following sections along with an example using the IODEF format and extensions. SOAP and the Web Services Security Model [19,20] are used to take advantage of existing standards for ease of implementation and integration of RID systems. Transport Layer Security (TLS) provides the necessary level of encryption for the transport RID messages. The Web Services WS-Security, WS-Policy, WS-Trust, and WS-Privacy specifications provide the standards based methods to encrypt and digitally sign SOAP messages, provide system use and privacy guidelines, authentication and authorization, encryption, as well as the method to establish trust between members of a RID consortium or a peering consortium. The Web Services Security Model will be used to provide the necessary security levels between peers on the RID network, whereas XML security functions like the digital signature and encryption can be used within the contents of the message for privacy and security in cases where certain elements must remain encrypted or signed as they traverse the PATH Moriarty Expires: August 28, 2004 [Page 19]
Internet-Draft February 28, 2004 of a trace. One example of this is the digital signature on the originatorÆs packet used for the trace request to provide a way to verify the identify the originator of the trace. The Web Services Security Model in relation to RID messaging will be expanded upon further with more specific detail in an upcoming draft release. 4.2.1 RID Messages using SOAP and Web Services Security Model Four RID message types are defined in this document to facilitate communications between CSIRTs or NPs. The message types include: Trace Request, Trace Authorization, Source Found, and Relay Request. 1. Trace Request. This message is sent to the Network Management Station next in the upstream trace. It may be used to initiate a trace request or to continue a trace request to an upstream network closer to the source of the origin of the security incident. 2. Trace Authorization. This message is sent to the initiating NMS from each of the upstream NP's NMS to provide information on the trace status in the current network. 3. Source Found. This message indicates that the source of the attack in this trace was located and is sent to the initiating NMS through the network of NMS systems in the path of the trace. 4. Relay Request. This message type is used when the source of the traffic is believed to be valid. The purpose of the relay message request is to leverage the existing peer relationships in order to notify the network provider closest to the source of the valid traffic of some event that has occurred, which may be a security related incident. When a system receives a RID message, it must be able to first determine the type of message it is and then parse it accordingly. SOAP and the WS-Security model will be used for this purpose and will be discussed further in an upcoming version of this draft. 4.2.2 RID Data Types RID is derived from the IODEF data model and inherits all of the data types defined in the IODEF model. With the exception of representing packet data, no other additional data types are required for RID extensions. The extension for RID containing the packet contents will be represented in a hexadecimal format for easier use by single network trace systems and integration with other aspects of the network. Hexadecimal data is defined in XML as the datatype: Moriarty Expires: August 28, 2004 [Page 20]
Internet-Draft February 28, 2004 xs:hexBinary Hexadecimal attributes are represented by the hexBinary data type. The hexBinary data type allows you to code binary content as a character string by translating the value of each binary octet into two hexadecimal digits. 4.2.4 IODEF-Document The IODEF model will be followed as specified in RFCXXXX (the RFC number will replace the XXXX when a number has been assigned for the document) for each of the RID message types. The AdditionalData element will be used to define extensions to the IODEF-Document in order to facilitate RID communications. Each message type varies slightly in format and purpose; hence the requirements vary and will be specified for each. All classes, elements, attributes, etc. that are defined in the IODEF-Document are valid in the context of a RID-Document, however certain classes, attributes, elements, etc. will be required for each message type and the rest are optional when sending a RID request and will be defined in sections 4.1.3. The IODEF model MUST be fully implemented to ensure proper parsing of all RID messages. Since RID documents are IODEF-Document with extensions, all RID documents contain the IODEF Document class, the IODEF model, and the IODEF DTD. The incident class is required for an IODEF-Document and in turn for a RID-Document. The AdditionalData attribute defined in the Incident class will be used to define the RID extensions for the IODEF model that are included in some RID messages. Please see RFCxxxx for specific information on the IODEF-Document requirements. (The RFC number will be defined when the document becomes an RFC). 4.2.5 IODEF-Document Extensions There are three extensions required to facilitate RID communications within the IODEF data model. The first extension is used to represent the data used in tracing an incident, the second is used to list out the path a trace has taken at the NMS or NP level, and the third is used to indicate the approval status of a trace or relay request. In order for network traffic to be traced across a network, an example packet from the attack must be sent along with trace or relay requests. All of the non-changing fields of an IP header along with 8 bytes of payload are required to provide enough information to uniquely trace the path of a packet. The non- changing fields of the packet header and the 8 bytes of payload are the superset of data required by most single network tracing systems used and prevent the need for sharing potentially sensitive Moriarty Expires: August 28, 2004 [Page 21]
Internet-Draft February 28, 2004 information that may be contained in the data portion of a packet. The AdditionalData will be used to create an extension of the IODEF model to include a hexadecimal formatted packet including all packet header information plus 8 bytes of payload. RID requires the first 28 bytes of an IP v4 packet in order to perform a trace. The required number of bytes provides the IP header in an IP V4 packet, which is 10 bytes long, the TCP/UDP/ICMP header is also 10 bytes long, plus an additional 8 bytes of payload to distinguish the packet for tracing purposes. RID requires 48 bytes for an IP V6 packet in order to distinguish the packet in a trace. The input mechanism should be flexible enough to allow intrusion detection systems or packet sniffers to be the source of the information. The system creating the RID message should also use the packet information to populate the Incident class information in order to avoid human error, but also allow a system administrator to override the automatically populated information. As required for an IODEF extension in (IODEF Section 4.2), the parameter entities for extensions to the IODEF model are defined here to allow for proper parsing of the required extensions to the IODEF model used in RID messages or documents. The definition contains the location of the extension DTD and references the entities: <!DOCTYPE IODEF-Document SYSTEM "/path/to/IODEF-Document.dtd" [ <!ENTITY % x-IPPacket SYSTEM "/path/to/RID-IPPacket.dtd"> <!ENTITY % x-NPPath SYSTEM "/path/to/RID-NPPath.dtd"> <!ENTITY % x-TraceStatus SYSTEM "/path/to/RID-Status.dtd"> %x-IPPacket; %x-NPPath; %x-TraceStatus; ]> The AdditionalData class from the IODEF model is extended to facilitate RID communications as follows: +------------------+ | AdditionalData | +------------------+ | ANY | | |<>---(0..*)----[ IPPacket ] | ENUM restriction | | ENUM type |<>---{1..*}----[ NPPath ] | STRING meaning | | |<>---(0..1)----[ TraceStatus ] +------------------+ Figure 3: the AdditionalData class extension The aggregate classes that constitute the RID extensions for the AdditionalData class are: Moriarty Expires: August 28, 2004 [Page 22]
Internet-Draft February 28, 2004 IPPacket Zero or many. The IP Packet that will be used to trace to the source of a security incident reported through RID. NPPath One or many. The contact information for the NPs involved in a trace, which includes information on the actual RID or NMS systems involved in the trace. TraceStatus Zero or One. This is used only in Type 2, Authorization Status messages to report back to the originating RID system if the trace will be continued by each NMS or RID system that received a trace request in the path to the source of the traffic. The attributes of the AdditionalData class as defined in the IODEF model. Specific meanings have been added for use as strings in the meaning attribute. restriction optional. Defined in section 3.2 of the IODEF model. Type Required. ENUM. The data type of the element content. The permitted values for this attribute are in the IODEF document. The default value is "string", and MUST be set to "xml" for all extensions to the IODEF model as stated in the IODEF Data Model (Section 4.2). Meaning Mandatory. STRING. An identifier used to determine which extension of the AdditionalData attribute is used. In the context of RID, the following identifiers are valid: 1. RID-IPPacket. The packet information used to trace attack traffic used for RID incident response. 2. RID-NPPath. The Network Providers in the path of a trace that was either the origin of the request or an NMS in the path of the trace. 3. RID-TraceStatus. Trace Status is used in the Type 2 message. It lists the response from the upstream provider that received either a Trace request (Type 1) or a Relay request (Type 4) message and notifies the originator of a request along with all NPs in the downstream path if the trace will continue in the current network that has received the request. 4.2.5.1 IPPacket Extension The IPPacket information will be represented through the AdditionalData class extension of IODEF. Moriarty Expires: August 28, 2004 [Page 23]
Internet-Draft February 28, 2004 +-----------------------+ | IPPacket | +-----------------------+ | ENUM restriction |<>-----------[ IPVersion ] | | | |<>-----------[ HexPacket ] | | | |<>---(0..*)--[ IPPacket ] +-----------------------+ Figure 4: the IPPacket class The aggregate classes that constitute the NPPath class are: IPVersion. One or Many. STRING. The IP version of the packet used in the trace. 1. IPv4 2. IPv6 HexPacket. HexBinary. A packet in hexadecimal format using the xs:hexBinary XML data type. 28 bytes for an IPv4 packet. 48 bytes for an IPv6 packet. IPPacket Zero or many. Recursive definition of IPPacket, allowing for grouping of data. This may be used if more than one example packet will be sent in a single trace or relay request. Moriarty Expires: August 28, 2004 [Page 24]
Internet-Draft February 28, 2004 4.2.5.2 NPPath Extension The path information will also be an extension of the AdditionalData class. +------------------+ | NPPath | +------------------+ | ENUM restriction |<>---{0..1}----[ name ] | | | |<>---{0..*}----[ RegistryHandle ] | | | |<>-------------[ Node ] | | | |<>---{0..*}----[ Email ] | | | |<>---{0..*}----[ Telephone ] | | | |<>---{0..1}----[ Fax ] | | | |<>---{0..1}----[ Timezone ] | | | |<>---{1..*}----[ NPPath ] +------------------+ Figure 5: the NPPath class The aggregate classes that constitute the NPPath class are: name Zero or one. NAME. The name of the contact. The contact may either be an organization or a person. The type attribute dictates the semantics (organization or person). RegistryHandle Zero or many. The handle name in a registry. Care must be taken to ensure that a handle is meaningful to the recipient. Intra-organizational handles are of not much use for extra-organizational communication. Node One. The Node class is used to identify a host or network device, in this case to identify the system communicating RID messages or the NPÆs NMS. The base definition of the class is reused from the IDMEF specification, see Section 4.2.7.1 of [7] in the IODEF specification IODEF 3.18. Email Zero or many. EMAIL. The email address of the contact formatted according to Section 2.2.12. Moriarty Expires: August 28, 2004 [Page 25]
Internet-Draft February 28, 2004 Telephone Zero or many. PHONE. The telephone number of the contact formatted according to documentation in Section 5.21 of RFC2256. Fax Zero or one. PHONE. The facsimile telephone number of the contact formatted according to documentation in Section 5.21 of RFC2256. Timezone Zero or one. STRING. The timezone in which the contact resides. NPPath One or many. Recursive definition of NPPath, allowing for grouping of data. This is necessary in order to provide the complete list of systems communicating in the RID trace or relay request. The first NPPath definition is used for the originating host and NP information, the second listing is for the first NP that receives a request. All subsequent entries are used to list the information for each RID system for the NPs involved in the trace that a request has been sent to. 4.2.5.3 TraceStatus Extension The TraceStatus information will also use AdditionalData. +-------------------+ | TraceStatus | +-------------------+ | | | ENUM restriction |<>-------[ AuthorizationStatus ] | | +-------------------+ Figure 6: the TraceStatus class The aggregate elements that constitute the TraceStatus class are: AuthorizationStatus Required. ENUM. The listed values are used to provide a response to the requesting CSIRT of the status of a trace request in the current network. 1. Approved. The trace was approved and will begin in the current NP. 2. Denied. The trace was denied in the current NP. The next closest NP can use this message to filter traffic from the upstream NP using the example packet to help mitigate the effects of the attack as close to the source as possible. The Type 2 message must be passed back to the originator and a Type 3 used from the closest NP to the source to indicate actions Moriarty Expires: August 28, 2004 [Page 26]
Internet-Draft February 28, 2004 taken. 3. Pending. Awaiting approval and a time-out period has been reached which resulted in this pending status and Type 2 message being generated. 4.3 RID Documents Defined by Message Type Derived from IODEF This section includes the mandatory IODEF information used in all RID messages. Since RID is a wrapper for an IODEF document, the full IODEF specifications should be implemented, but the following section identifies the IODEF fields that must be filled in when generating a RID message or document. Other fields may optionally be filled in to provide further information to an incident handler and thus must be implemented for proper parsing of a RID message wrapping an IODEF document. This section will reference the IODEF model and the sections of the IODEF RFC where each IODEF class can be located. Incident Class (IODEF 3.2) Purpose: The Purpose will always be 1. Handling for RID messages Restriction: Sender can select from the IODEF specifications for this value and fill in as appropriate IncidentID (IODEF 3.3) GUID: Name of CSIRT or NP that created the document Alternate ID (IODEF 3.4) This incident ID is one set by another CSIRT that is tracking the same or a similar incident. This value should not be set in the initial request, but may be set in a request passed forward by an NP in the path of a trace. Related Activity Class (IODEF 3.5) This class is optional if an AlternateID is specified, otherwise it is unnecessary. IncidentData Class (IODEF 3.7) Description: Text description of the incident - Mandatory for RID Assessment: Characterization of the impact - Mandatory for RID, (reference IODEF section 3.12) Impact aggregate class (IODEF 3.12.1) MUST be used along with the Confidence class (IODEF 3.12.5) in the Assessment Class. The other impact classes are optional and may depend on the Incident type to determine if the additional classes are appropriate. Method: Techniques used in attack - Optional for RID (IODEF 3.11) DetectTime: Mandatory for RID (Time Class - IODEF 2.26 and 3.9) StartTime: Mandatory for RID (Time Class - IODEF 2.26 and 3.9) EndTime: Optional for RID, incident may still be in process in which no end time can be listed (Time Class - IODEF 2.26, 3.9) ReportTime: Mandatory for RID (Time Class - IODEF 2.26 and 3.9) Moriarty Expires: August 28, 2004 [Page 27]
Internet-Draft February 28, 2004 Contact: Mandatory for RID (IODEF 3.8) The required aggregate classes for the contact class in RID messages include: Name, RegistryHandle (IODEF 3.8.1), Email, Telephone The attributes in the contact class are required in the IODEF document and thus are required in RID messages and include: Restriction, Role, and Type Expectation: Mandatory for RID (IODEF 3.10) The following attributes are required in RID messages: Priority and Category Note: Although Category is required in a request, the NP closest to the source of the attack decides upon the ultimate response. History: Required for upstream trace relays or requests, but not For the original request, (IODEF 3.13). May also be used to Further describe actions taken along the NP Path of a trace. EventData: Required for RID (IODEF 3.14 - 3.16) Much of the EventData Class is a duplicate for the aggregate IncidentData class and the proper uses of this class are defined in the IODEF RFC. System class (IODEF 3.17) The System class is required and the information listed in this class can be automatically entered into this class from the packet used in the incident trace by the RID implementation. Information must be reviewed by the submitter and the additional required classes and attributes filled in for proper processing of a request. The system class MUST be used to list the source and the target or intermediate system(s) and MUST note if the system was spoofed through the use of the Node class (IODEF 3.18). A separate instance of the System class (and Node Class) is used for each type of system listed in the document. The spoof section MUST be used in the System EventData Class of all RID messages and is set to the value of spoofed for all requests (Type 1) that require an actual trace of network traffic. In a Type 4 Relay Request, the source is believed to be valid. All other classes of the System Class are optional as in the IODEF document. AdditionalData: RID messages require that the NP Path and the IPPacket extensions are used to provide adequate information for an upstream peer to perform a trace. The information contained in the NPPath and IPPacket extensions must remain and be maintained in each RID message type document. The TraceStatus extension is used in message type 2 alone since it's purpose is to let the downstream NP know if the trace was approved and will begin in the next upstream network. IPPacket (IP version of packet to be traced) NPPath (Original Request should contain originator plus the next peer in the upstream request, the host that is receiving the request) Moriarty Expires: August 28, 2004 [Page 28]
Internet-Draft February 28, 2004 TraceStatus (Approval status for the trace in the current network) Restriction Optional. ENUM. The IODEF restriction should be used in addition to the RID privacy and security guidelines since this is optional on the part of the receiving end of an IODEF message and is not enforced. Note: The implementation of the RID system may obtain some of the information needed to fill in the content required for each message type automatically from packet input to the system or default information such as that used in the NPPath extension. 4.3.1 Trace Request Description: This message or document is sent to the Network Management Station next in the upstream trace once the upstream Source of the traffic has been identified. The following information is required for message type 1 and will be provided through: RID Wrapper identifying Message Type 1 Time Stamps (DectectTime, StartTime, EndTime, ReportTime) Incident Identifier (Incidnent Class, IncidentID) Trace number - used for multiple traces of a single Incident, must be noted Confidence rating of Security Incident (Impact and Confidence Class) System Class is used to list both the Source and Destination Information used in the attack and must note if the traffic is spoofed, thus requiring an upstream trace request in RID Packet used to trace incident across the network IPPacket extension for RID Path information of Network Management Systems used in the trace NPPath extension for RID [Free form test area for any additional information on justification for relay message request, IODEF IncidentData Description] Digital signature from initiating NMS, passed to all systems in upstream trace using XML digital signature A DDoS attack can have many sources resulting in multiple traces to locate the sources of the attack. It may be valid to continue multiple traces for a single attack. The path information would enable the administrators to determine if the exact trace had already passed through a single network. The incident identifier must also be used to identify multiple trace requests from a single incident. Moriarty Expires: August 28, 2004 [Page 29]
Internet-Draft February 28, 2004 4.3.2 Trace Authorization Message Description: This message is sent to the initiating NMS from the next upstream NP's NMS to provide information on the trace status in the current network. The following information is required for Message Type 2 and will be provided through: RID Wrapper identifying Message Type 2 Time Stamps (DectectTime, StartTime, EndTime, ReportTime) Incident Identifier (Incidnent Class, IncidentID) Trace number - used for multiple traces of a single Incident, must be noted Confidence rating of Security Incident (Impact and Confidence Class) Status of trace request TraceStatus extension for RID Packet used to trace incident across the network IPPacket extension for RID Path information of Network Management Systems used in the trace NPPath extension for RID The last NP listed is the NP sending this Type 2 message. All previous NPs listed in the NPPath must be retained. Digital signature of responding NP for authenticity of Trace Status Message, from the NP creating this message using XML digital signature [Additional free form text information on the attack, History Class] A message is sent back to the NMS that initiated the trace as a notification means. This message verifies that the next NMS in the path has received the message from the previous NMS in the path. This message also verifies that the trace is now continuing, stopped or pending in the next upstream network in the path of the trace. The pending status would be automatically generated after a 2-minute timeout without system predefined or administrator action taken to approve or disapprove the trace continuance. Moriarty Expires: August 28, 2004 [Page 30]
Internet-Draft February 28, 2004 4.3.3 Source Found Message Description: This message indicates that the source of the attack in this trace was located and is sent to the initiating NMS through the network of out-of-band NMS systems in the path of the trace. The following information is required for Message Type 3 and will be provided through: RID Wrapper identifying Message Type 3 Time Stamps (DectectTime, StartTime, EndTime, ReportTime) Incident Identifier (Incidnent Class, IncidentID) Trace number - used for multiple traces of a single Incident, must be noted Confidence rating of Security Incident (Impact and Confidence Class) Action Taken (Expectation and Category Class) Packet used to trace incident across the network IPPacket extension for RID Path information of Network Management Systems used in the trace NPPath extension for RID The last NP listed is the NP, which located the source of the traffic (the NP sending the Type 3 message) [Free form test area for any additional information on The identified source of the attack traffic, IODEF Description, Incident Class] Digital signature of source NP for authenticity of source found Message, the NP creating this message using XML digital signature [True Source address and other information on the attack, History Class] A message sent back to initiating NMS to notify the originating network administrators that the source has been located. The actual source information may or may not be included depending on the policy of the network in which the client or host is attached. Any action taken by the NP to act upon the discovery of the source of a trace should be included. The NP may be able to automate the adjustment of filters at their border router to block outbound access for the machine(s) discovered as a part of the attack. The filters may be as comprehensive as to block all Internet access until the host has taken the appropriate action to resolve any security issues or to rate limit the ingress traffic as close to the source as possible. Security and privacy considerations discussed later must be taken into account with source found messages. Note: The Category Class may be expanded in IODEF at a later date Moriarty Expires: August 28, 2004 [Page 31]
Internet-Draft February 28, 2004 to accommodate all of the possible actions taken as a result of a RID trace or relay request. Until that time occurs, the History class should be used to note all actions taken close to the source of a trace. The additional options include, but may not be limited to: Action Taken (multiple selections permitted) ______________________________________________ No action at this time Filter at upstream peer ingress point Rate Limit attack traffic Network segment blocked Host (IP Address) blocked from Internet access Protocol port used in attack blocked Alert generated Site notified Other 4.3.4 Relay Message Request Description: This message type is used when the source of the traffic is believed to be valid. The purpose of the relay message request is to leverage the existing bi-lateral peer relationships in order to notify the network provider closest to the source of the valid traffic of some event that has occurred, which may be a security related incident. The following information is required for Message Type 4 and will Be provided through: RID Wrapper identifying Message Type 4 Time Stamps (DectectTime, StartTime, EndTime, ReportTime) Incident Identifier (Incidnent Class, IncidentID) Trace number - used for multiple traces of a single Incident, must be noted Confidence rating of Security Incident (Impact and Confidence Class) Packet used to trace incident across the network IPPacket extension for RID Path information of Network Management Systems used in the trace NPPath extension for RID [Free form test area for any additional information on justification for relay message request, IODEF Description] Digital signature from initiating NMS, passed to all systems in upstream trace using XML digital signature Security considerations would include the ability to encrypt the contents of the relay message request using the public key of the destination network provider. The incident number would increase as if it were a trace request message in order to ensure Moriarty Expires: August 28, 2004 [Page 32]
Internet-Draft February 28, 2004 uniqueness within the system. The relaying peers would also append their AS information as the request message was relayed along the web of network providers so that the source found message could utilize the same path as set of trust relationships for the return message, which would indicate any actions taken. The request would also be recorded in both the state table of the initiating and destination NP NMS. The destination NP would be responsible for any actions taken as a result of the request in adherence to any service level agreements or internal policies. The NP should confirm the traffic actually originated from the suspected system before taking any action and confirm the reason for the request. Note: The AS number of the source IP address is listed as the first AS in the path information for the NMSs. The last relay packet sent to the source AS will include the same path information twice. The AS information is necessary in order to direct the message appropriately to the closest NP to the source of the traffic. In the case of message type 4, the filter information may be encrypted, so the relaying NMSs may have no other way to determine how to direct the packets. Moriarty Expires: August 28, 2004 [Page 33]
Internet-Draft February 28, 2004 4.3.5 Example Upstream Trace The diagram below outlines the RID-DOS communication between NMS systems on different networks tracing an attack. Attack Dest NP-1 NP-2 NP-3 Attack Src 1. Attack | Attack reported | detected 2. Initiate trace 3. Locate origin through upstream NP. 4. o---Msg-Type-1------> 5. Trace Initiated 6. <-----Msg-Type-2----o 7. Locate origin through upstream NP. 8. o---Msg-Type-1---> 9. Trace Initiated 10. <------------Msg-Type-2------------o 11. Locate attack source on network X 12. <------------Msg-Type-3------------o Figure 7: RID Communication Flow The NP who detected the attack initiates the trace. The attack is traced to the source or the next upstream NP. This process continues until the trace identifies the source of the attack. Any type 2 and 3 messages must pass through all NMS systems in the path back to the initiator of the trace because of the secure connections established between NMS systems of border networks. The involved systems in the path for type 2 and 3 messages would then have the ability to see the acknowledge the trace status before sending the messages back along the NMS path to the originating NMS. Before a trace can be initialized, the originating NMS must check an internal database to determine if a trace to the same IP address or network address has occurred within a specified period of time, no less than 1 day. The trace may have also been initiated by the same NMS or this NMS may have been in the path of the trace. The previous filter must be maintained for a minimum of a one-week period in order to retrieve the filter for comparison before initiating a trace request or allowing a trace continuance to occur. If the network administrator justifies a similar trace, a note might be added to the Description element of the document to provide an additional confidence indication to the upstream NPs in Moriarty Expires: August 28, 2004 [Page 34]
Internet-Draft February 28, 2004 the path of the trace. A single trace may be limited in time by factors determined by the single network trace system used by the NPs in the path of the trace. The single trace system may either trace a packet dynamically or search through stored packet data for evidence that the packet had traversed the network. In the case of a dynamic trace, the traffic would need to be active on the network for the trace to be successful or the trace would cease and a message would be sent to indicate the status that the trace cannot continue to the originating NMS through the consortiumÆs or bilateral trust relationships formed by the RID or NMS systems in the path of the trace. The packet trace may also be limited due to the storage space on networks, which save traffic data. A trace status message would be sent in this case as well to provide the path information up to the point in which the trace could no longer be continued to the originator of the trace through the RID systems in the path of the trace. This information could also be used to block or mitigate the traffic at the participating NP closest to the source. 4.3.6 RID Trace Request Example The example listed is of a trace request, based on the incident report example from the IODEF document. The AdditionalData extensions were added as appropriate for a Trace Request message using the IPPacket and NPPath classes. The example given is that of a CSIRT reporting a DoS attack in progress to the upstream NP. The request asks the next NP to continue the trace and have the traffic mitigated closer to the source of the traffic. <IODEF-Document version="1.0"> <Incident restriction="need-to-know" purpose="handling"> <IncidentID name="CERT-FOR-OUR-DOMAIN">CERT-FOR-OUR-DOMAIN#207-1 </IncidentID> <IncidentData> <Description>Host involved in DOS attack</Description> <StartTime>2004-02-02T22:19:24+00:00</StartTime> <DetectTime>2004-02-02T22:49:24+00:00</DetectTime> <ReportTime>2004-02-02T23:20:24+00:00</ReportTime> <Expectation category="other"> <Description>Rate limit traffic close to source</Description> </Expectation> <Assessment> <Impact severity="low" completion="failed" type="none"></Impact> </Assessment> <Contact role="creator" role="irt" type="organization"> <name>CSIRT-FOR-OUR-DOMAIN</name> <Email>csirt-for-our-domain@ourdomain</Email> </Contact> Moriarty Expires: August 28, 2004 [Page 35]
Internet-Draft February 28, 2004 <Contact role="tech" type="organization"> <name>Constituency-contact for 10.1.1.2</name> <Email>Constituency-contact@10.1.1.2</Email> </Contact> <History> <HistoryItem type="notification"> <IncidentID name="CSIRT-FOR-OUR-DOMAIN">CSIRT-FOR-OUR-DOMAIN#207-1 </IncidentID>CERT-FOR-OUR-DOMAIN <Description>Notification sent to next upstream NP closer to 10.1.1.2</Description> <DateTime>2001-09-14T08:19:01+00:00</DateTime> </HistoryItem> </History> <EventData> <System category="source"> <Service> <port>38765</port> </Service> <Node> <Address category="ipv4-addr">10.1.1.2</Address> </Node> </System> <System category="target"> <Service> <port>80</port> </Service> <Node> <Address category="ipv4-addr">192.168.1.2</Address> </Node> </System> </EventData> </IncidentData> <AdditionalData type="xml"> <RID-IPPacket:RID-IPPacket> xmlns:RID="http://www.ietf.org/iodef/RID-IPPacket.html" xmlns="http://www.ietf.org/iodef/RID-IPPacket.html"> <IPPacket> <IPVersion>IPv4</IPVersion> <HexPacket>(Hex Binary of Packet contents)</HexPacket> </IPPacket> </RID-IPPacket:RID-IPPacket> </AdditionalData> <AdditionalData type="xml"> <RID-NPPath:RID-NPPath> xmlns:RID="http://www.ietf.org/iodef/RID-NPPath.html" xmlns="http://www.ietf.org/iodef/RID-NPPath.html"> <NPPath> <Name>CSIRT-FOR-OUR-DOMAIN</Name> <RegistryHandle>CSIRT123</RegistryHandle> <Email>csirt-for-our-domain@ourdomain</Email> <Node> Moriarty Expires: August 28, 2004 [Page 36]
Internet-Draft February 28, 2004 <Address category="ipv4-addr">172.17.1.2</Address> </Node> </NPPath> <NPPath> <Name>CSIRT-FOR-UPSTREAM-NP</Name> <RegistryHandle>CSIRT345</RegistryHandle> <Email>csirt-for-upstream-np@ourdomain</Email> <Node> <Address category="ipv4-addr">172.20.1.2</Address> </Node> </NPPath> </RID-NPPath:RID-NPPath> </AdditionalData> </Incident> </IODEF-Document> <-- Digital Signature applied to the packet using the XML Digital Signature W3C Recommendations. This will be fixed to provide a proper example in the upcoming draft release. <Signature ID?> <SignedInfo> <CanonicalizationMethod/> <SignatureMethod/> (<Reference URI? > (<Transforms>)? <DigestMethod> <DigestValue> </Reference>)+ </SignedInfo> <SignatureValue> (<KeyInfo>)? (<Object ID?>)* </Signature> --> 5. RID IODEF Extension Document Type Definition <?xml version="1.0" encoding="UTF-8"?> <!-- ***************************************************************** ***************************************************************** *** RID Extension XML DTD to the *** *** IncidentData Exchange Format XML DTD *** *** Version 01, February 2004 *** ***************************************************************** ***************************************************************** --> <!ENTITY % attlist.rid " version CDATA #FIXED '0.20' Moriarty Expires: August 28, 2004 [Page 37]
Internet-Draft February 28, 2004 "> <!-- ================================================================ == Element definitions == ================================================================ --> <!-- ================================================================ === AdditionalData class - RID Extensions === === - IPPacket === - NPPath === - TraceStatus ================================================================ --> <!ELEMENT AdditionalData (IPPacket*, NPPath+, TraceStatus?)> <!ATTLIST AdditionalData restriction %attvals.restriction; #IMPLIED type %attvals.dtype; #REQUIRED meaning CDATA #IMPLIED > <!- ================================================================ == IPPacket class == === - IPVersion === - HexPacket ================================================================ --> <!ELEMENT IPPacket (IPVersion, HexPacket)> <!ATTLIST IPPacket restriction %attvals.restriction; #IMPLIED > <!ELEMENT IPVersion (#PCDATA)> <!ùFor the purpose of RID, the packet should be logged without being decoded to ensure each trace system will receive the identical packet. The packet must not be decoded when listed in the IPPacket class to ensure compatibility with single network trace Systems and other network components. This element is represented in hexBinary. The length MUST be specified to the appropriate size for an IPv4 packet (28 bytes) and an IPv6 packet (48 bytes). The length listed for the data type hexBinary is listed in bytes. --> <!ELEMENT HexPacket (raw)> <!-- =================================================================== === NPPath class === === - Name Moriarty Expires: August 28, 2004 [Page 38]
Internet-Draft February 28, 2004 === - RegistryHandle === - Node (Node class in IODEF Model Section 3.18) === - Email === - Telephone === - Fax === - TimeZone === - NPPath (recursive) =================================================================== --> <!ELEMENT NPPath (Name?, RegistryHandle*, Node, Email*, Telephone*, Fax?, TimeZone?, NPPath+)> <!ATTLIST NPPath restriction %attvals.restriction; #IMPLIED > <!ELEMENT Name (#PCDATA)> <!ELEMENT RegistryHandle (#PCDATA)> <!ATTLIST RegistryHandle type %attvals.registrytype; "local" > <!ELEMENT Email (#PCDATA)> <!ELEMENT Telephone (#PCDATA)> <!ELEMENT Fax (#PCDATA)> <!-- =================================================================== === TraceStatus class === === - AuthorizationStatus =================================================================== --> <!ELEMENT TraceStatus (ApprovalStatus)> <!ATTLIST TraceStatus restriction %attvals.restriction; #IMPLIED > <!ELEMENT AuthorizationStatus (#PCDATA)> Moriarty Expires: August 28, 2004 [Page 39]
Internet-Draft February 28, 2004 6. Message Transport RID messages or documents can be transported over existing protocols since the messages are in an XML format using the IODEF model. The privacy and security considerations are such that a means to encrypt and sign the data must be provided. Encrypting or signing the documents may be done within the capabilities of XML, as defined in the IODEF specification. The use of transport protocols to encrypt data such as S/MIME and HTTPS are encouraged to provide an additional level of security, integrity, and authentication. The encryption requirements and considerations for RID are discussed in the Security section of this document. 6.1 Message Delivery Protocol - Integrity and Authentication The RID protocol must be able to guarantee delivery and meet the necessary security requirements of a state-of-the-art protocol. In order to guarantee delivery, TCP should be considered as the underlying protocol within the current network standard practices. It may seem appropriate to use SNMP trap messages since Network Management Systems already use this messaging structure. However, RFC1215 discourages the use of traps for this type of application and attempts to discourage the creation of new trap types. The current trap messaging structure does not satisfy the information requirements in order to successfully carry out a trace. Trap messages are sent via UDP, which assist in the quick delivery of packets, however they do not guarantee delivery as in TCP. The RID protocol for inter-NMS communication could provide the transport mechanism for message delivery. Security considerations must include the integrity, authentication, privacy, and authorization of the messages sent between RID communication or NMS systems. The communication between RID systems must be authenticated and encrypted to ensure the integrity of the messages and the RID systems involved in the trace. Another concern that needs to be addressed is authentication for a request that traverses multiple networks. In this scenario, systems in path of the multi-hop trace request need to authorize a trace from not only their neighbor network, but also from the initiating NMS. Several methods can be used to ensure integrity and privacy of the communication. The transport mechanism selected (S/MIME, HTTP, HTTPS, etc.) may be agreed upon by a consortium using the RID protocol to ensure consistency among the peers. Consortiums may vary their selected transport mechanisms and thus must decide up on a mutual protocol to use for transport when communicating with peers in a neighboring consortium using RID. RID systems MUST support both the S/MIME and HTTPS protocols and properly integrate with a public key infrastructure (PKI) managed by the consortium, other protocols are optional for implementation. Consortiums are discussed later in the paper. Moriarty Expires: August 28, 2004 [Page 40]
Internet-Draft February 28, 2004 6.2 Transport Communication Out-of band communications dedicated to NP interaction for RID messaging would provide additional security as well as guaranteed bandwidth during a denial of service attack. This might be accomplished through logical paths defined over the existing network. Out-of-band communications may not be possible between all network providers, but should be considered if feasible to protect the network management systems used for RID messaging on the network. In order to address the integrity and authenticity of messages, transport encryption MUST be used to secure the traffic sent between RID or NMS systems with pre-defined trust relationships. Systems with predefined relationships for RID would include those who peer in a consortium with agreed upon appropriate use regulations and for peering consortiums to link together a larger group of networks. Systems used to send authenticated RID messages between networks MUST use a dedicated and secured interface to connect to a border Network's RID system. If a single system is used to connect to multiple RID systems or NMS(s), each connection must have a dedicated interface and the security requirements MUST meet those agreed upon through the consortium regulations, peering, or service level agreements (SLA). The NMS interface must only listen for and send RID messages over an encrypted tunnel and meeting a minimum requirement of algorithms and keys established by the consortium, peering, or SLA agreement. Transport Layer Security (TLS) or Secure MIME are appropriate protocols to provide the necessary level of security and are established standards. The selected algorithm must have minimum security levels of the times, 3DES or 128-bit AES are sufficient at the time this draft was written. The encryption strength must adhere to import and export regulations of the involved countries of a data exchange. 6.3 Authentication of RID Protocol In order to insure the authenticity of the RID messages, a message authentication scheme using a public key infrastructure (PKI) must be inherent to the protocol. SOAP tied together with WS-Security requires a trust center such as a PKI or Kerberos key distribution center for the distribution of credentials to provide the necessary levels of security for this protocol. Public key certificates pairs issued by a trusted Certificate Authority (CA) will be used to provide the necessary level of authentication and encryption for the RID protocol. The CA used for RID messaging must be trusted by all involved parties and may take advantage of similar efforts, such as the dot-root project (http://dot-root.com). The PKI infrastructure used for authentication would also provide the necessary certificates needed for encryption via either Transport Layer Security (TLS) used in Moriarty Expires: August 28, 2004 [Page 41]
Internet-Draft February 28, 2004 the HTTPS protocol or Secure MIME (S/MIME). Hosts receiving a RID message, such as a trace request, for example, must be able to verify that the sender of the request is valid and trusted. Using digital signatures on a hash of the RID message with an X.509 version 3 certificate issued by a trusted party can be used to authenticate the request. The X.509 version 3 specifications as well as the digital signature specifications and Certificate Revocation List (CRL) Internet standards set forth in RFC2459 must be followed in order to interoperate with a PKI designed for similar Internet purposes. The IODEF specification must be followed for digital signatures to provide the authentication and integrity aspects required for secure messaging between network providers. The use of digital signatures in RID XML messages MUST follow the World Wide Web Consortium (W3C) recommendations for signature syntax and Processing when either the XML encryption or digital signature are used within a document. Web Services Security (WS-Security) MUST be followed for encryption and digital signatures on the SOAP messaging. An optional extension to the authentication scheme would be to incorporate the use of attribute certificates to provide authorization capabilities as described in RFC3281. This may be useful as messages are sent from network peers to determine authorization levels based on the attribute information in the certificate, which could be used to determine priority of a trace request. The attribute information might be used to determine if a trace request should be processed automatically or if human intervention is required. The WS-Policy specifications will be used for the policy verification, which may determine if a trace will be continued. 6.4 Authentication Considerations for a Multi-hop Trace Request Bilateral trust relations between network providers ensure the authenticity of requests for trace requests from immediate peers in the web of networks formed to provide the trace back capability. A network provider several hops into the path of the RID trace must trust the information from their peer as to the confidence rating of the attack and the previous trust relationships in the downstream path. In order to provide a higher assurance level as to the authenticity of the trace request, the originating NMS is included in the trace request along with contact information as well as the information of all NMS systems in the path the trace has taken. A second measure MUST be taken to ensure the identity of the originating NMS. The originating NMS, also listed as originator of the request in the path information, MUST include a digital signature in the trace request sent to all systems in the NMS upstream path. The initiating NMS system is required to include Moriarty Expires: August 28, 2004 [Page 42]
Internet-Draft February 28, 2004 a digitally signed hash of the packet filter information, all necessary fields of the IP header and 8 bytes of payload, in the trace request. This digital signature from the originating RID or NMS system is performed on the IPPacket class of the RID extension to the IODEF model in the AdditionalData class following the XML digital Signature specifications from W3C [17]. The signature MUST be passed to all parties that receive a trace request and each party MUST be able to validate the digital signature. In order to accommodate that requirement, the element HexPacket that MUST also remain unchanged as a request is passed along between providers is the only element for which the signature is applied. A second benefit to this requirement is that the integrity of the filter used is ensured as it is passed to subsequent NPs in the upstream trace of the packet. The trusted PKI used to provide authentication listed in the authentication section will also provide the certificates used to digitally sign the necessary information in the trace requests to meet the requirement of authenticating the original request. Since the CA is known and trusted by all parties, any host in the path of the trace can verify the digital signature. The digitally signed hash of the packet MUST be included in all upstream trace requests to allow subsequent NPs to verify the authenticity of a trace request. 6.4.1 Public Key Infrastructures and Consortiums Consortiums of NPs are an ideal way to establish a communication web of trust for RID messaging. The consortium could provide centralized resources, such as a PKI, and established guidelines for use of the RID protocol. The consortium would also assist in establishing trust relationships between the participating NPs to achieve the necessary level of cooperation and experience sharing among the consortium entities. The consortium may also be used for other purposes to better facilitate communication among NPs in a common area (Internet, region, government, education, private networks, etc.). Using a PKI to distribute certificates used by RID systems provides an already established method to link trust relationships between NPs of consortiums that would peer with NPs belonging to a separate consortium. In other words, consortiums could peer with other consortiums to enable communication of RID messages between the participating NPs. The PKI along with Memorandum of Agreements could be used to link border directories to share public key information in a bridge, hierarchy, or a single cross certification relationship. Consortiums also need to establish guidelines for each participating NP to adhere to. The guidelines MUST include: O Physical and practices to protect RID systems O Network and application layer protection for RID systems and communications Moriarty Expires: August 28, 2004 [Page 43]
Internet-Draft February 28, 2004 O Proper use guidelines for RID systems, messages, and requests O A PKI to provide authentication, integrity, and privacy 6.5 Privacy Concerns and System Use Guidelines Privacy issues raise many concerns when information sharing is required to achieve the goal of stopping or mitigating the affects of a security incident. The Web Services Security Model, specifically the WS-Policy and WS-Privacy specifications will be used to automate the enforcement of the privacy concerns listed within this document. The privacy and system use concerns that MUST be addressed in the RID system and other integrated components include: o Privacy of data monitored and/or stored on IDS for attack detection o Privacy of data monitored and stored on systems used to trace traffic across a single network o Privacy of the identity of a host used in an attack o Privacy of information such as the source and destination used for communication purposes over the monitored or RID connected network(s) o Protection of data from being viewed by intermediate parties in the path of a relay request MUST be considered o System use restricted to security incident handling within the local regionÆs definitions of appropriate traffic for the network monitored and linked via RID in a single consortium also abiding by the consortiums use guidelines o System use prohibiting the consortiumÆs participating NPs from inappropriately tracing non attack traffic to locate sources or mitigate traffic unlawfully within the jurisdiction or region o System use between peering consortiums MUST also adhere to any government communication regulations that apply between those two regions, such as encryption export and import restrictions o System use between consortiums MUST not request traffic traces and actions beyond the scope intended and permitted by law or inter-consortium agreements o System use between consortiums MUST respect national boundary issues and limit requests to appropriate system use and not to achieve their own agenda to limit or restrict traffic that is otherwise permitted within the country in which the peering consortium resides RID is useful when trying to determine the true source of a packet when it traverses multiple networks or to provide a means to communicate security incidents and a way to automate the response. In order to identify the source and trace multiple networks, the packet header information along with 8 bytes of payload are used in the packet identification. The information obtained from the trace may determine the identity of the source host or the network provider used by the source of the traffic. It should be noted that the trace mechanism used across a single network provider may Moriarty Expires: August 28, 2004 [Page 44]
Internet-Draft February 28, 2004 also raise privacy concerns for the clients of the network. Methods that may raise concern include those which involve storing packets for some length of time in order to trace packets after the fact. Monitoring networks for intrusions and for tracing capabilities also raise concerns for potentially sensitive valid traffic that may be traversing the monitored network. IDS and single network tracing is outside of the scope of this document, but the concern should be noted and addressed within the use guidelines of the network. Some IDS and single network trace mechanisms attempt to properly address these issues. RID is designed to pass the information needed by any single network trace mechanism used. The decision of what single trace mechanism used by a provider may depend on resources, existing solutions, and local legislation. Privacy concerns in regard to the single network trace must be dealt with at the client to network provider level and are out of the scope for RID messaging. The identity of the true source of an attack packet being traced trough RID could be sensitive. The true identity listed in a type 3 or source found message could be protected through the use of encryption on the fields containing the identity for the originating NP to decrypt or depending on SLAs, the action taken may be listed without the identity being revealed to the originating NP. The ultimate goal of the RID communication system is to stop or mitigate attack traffic and not to ensure the identity of the attack traffic is known to all involved parties including the site under attack. The NP that identifies the source would need to deal directly with the involved parties and proper authorities in order to determine the guidelines for the release of such information if it was regarded as sensitive. In some situations, systems used in attacks are compromised by an unknown source and then in turn are used to attack other systems. In this type of situation, the reputation of a business or organization may be at stake and the action taken listed in the RID message may be the only additional information reported in the source found message to the originating system. If the security incident was a minor incident such a zombie system used in part of a large-scale DDoS attack, ensuring the system is taken off the network until it has been fixed may be sufficient. The textual descriptions should include details of the incident in order to protect the reputation of the unknowing attacker and prevent the need for additional investigation where applicable. Local, state, or national laws may dictate the appropriate reporting action for specific security incidents. The packet information is sent across multiple networks that happen to be in the path of a trace could be seen as sensitive to the parties involved. A specific example of this concern may be that an attack occurred between a specific source and destination and every network provider in the path of the trace would now be aware that the cyber attack occurred. In cases where compromised systems are responsible for the attack, this may not raise privacy Moriarty Expires: August 28, 2004 [Page 45]
Internet-Draft February 28, 2004 concerns. However, in a targeted attack it may not be desirable for the knowledge of two nation states battling a cyber war to become general knowledge to all intermediate parties. However, it is important to allow the traces to take place in order to cease the activity since the health of the networks in the path could also be at stake during the attack. This provides a second argument for allowing the third message type, source found, to only include an action taken and not the identity of the offending host. In the case of a relay request, where the originating NP is aware of the NP that will receive the request for processing, the free form text areas of the document could be encrypted using the public key of the destination NP to ensure that no other NP in the path can read the contents. The encryption would be accomplished through the W3C specifications for encrypting an element. In some situations, all network traffic of a nation may be granted through a single network provider. In order to gain support for tracing mechanisms, options must also include the ability to send a source found message from the downstream peer of the network provider where the source was found to provide another layer of protection to the attack source identity. This provides an additional level of abstraction to hide the identity and the NP of the identified source of the traffic. Legal action may override this technical decision after the trace has taken place, but that is out of the technical scope of this document. Privacy concerns when using message type 4 to request action close to the source of valid attack traffic needs to be considered. Although the intermediate NPs would relay the request to the closest NP to the source, the intermediate NPs would not require the ability to see the contents of the packet or the text Description field(s) in the request. This message type does not require any action by the intermediate RID systems, except to relay the packet to the next NP in the path. Therefore, the contents of the request may be encrypted. The intermediate NPs would only need to know how to direct the request to the manager of the AS number in which the source IP address belongs. Traces must be legitimate security related incidents and not used for purposes such as sabotage or censorship. An example of such abuse of the system would include a request to block or rate limit legitimate traffic to prevent information from being shared between users on the Internet (restricting access to online versions of papers) or restricting access from a competitor's product in order to sabotage a business. Inter-consortium RID communications raise additional issues especially where the peering consortiums reside in different regions or nations. Trace requests and requested actions to mitigate traffic must adhere to the appropriate use guidelines and yet prevent abuse of the system. First, the peering consortiums MUST identify the types of traffic that can be traced between the Moriarty Expires: August 28, 2004 [Page 46]
Internet-Draft February 28, 2004 borders of the participating NPs of each consortium. The traffic traced should be limited to security incident related traffic. Second, the traces permitted within one consortium if passed to a peering consortium may infringe upon the peering consortiumÆs freedom of information laws. An example of this would be that a consortium in China may permit a trace of spam containing objectionable material, outlawed within the country. The RID trace may be a valid use of the system within the confines of the network border, but MUST not be permitted to continue across network boundaries where such content is permitted under law and could have the effect of restricting access to data unnecessarily. A continued trace into another country may break the laws and regulations of that nation. Any such traces MUST cease at the country's border. The privacy concerns listed in this section have addressed issues of privacy among the trusted parties involved in a trace within an NP, a RID consortium, and peering RID consortiums. Data used for RID communications must also be protected from parties that are not trusted. This protection is provided though the authentication and encryption of documents as they traverse the path of trusted servers. Each RID system MUST perform a bi-directional authentication when sending a RID message and use the public encryption key of the upstream or downstream peer to send a message or document over the network. This means that the document is decrypted and re-encrypted at each RID system either via S/MIME or TLS over HTTPS. The RID messages must be decrypted at each RID system in order to properly process the request or relay the information. Today's processing power is more than sufficient to handle the minimal burden of encrypting and decrypting relatively small typical RID message. 7. Security Considerations Communication between NP's RID or NMS systems must be protected. An out of band network, either logical or physical would prevent outside attacks against NMS communication. An out of band connection would be ideal, but not necessarily practical. By using authenticated encryption tunnels between RID systems the data in transit would be protected as well as to ensure the integrity of the data and MUST be used. In the case where the RID network forms a bilateral interconnection of adjacent peers, the RID systems would permit messages between peering networks, which would relay messages to upstream peers on behalf of the initiating network peer. The trust would be based on consortiums and established trust relationships of PKI cross certifications of consortiums. By using SOAP, Web Services Security Model, Transport Layer Security, and the XML security features of encryption and digital signatures, RID takes advantage of existing security standards. The standards provide clear methods to ensure messages are secure, authenticated, authorized, meet policy and privacy guidelines, and Moriarty Expires: August 28, 2004 [Page 47]
Internet-Draft February 28, 2004 integrity is maintained. Policies between NPs must be established to provide guidelines for communication. The policy should include communication methods, security, and fall-back procedures. The Policy should establish a method to protect communications of RID systems between all bordering NPs. The trust relationships would have to extend to all bordering NPs in order to be successful in tracing and stopping attacks. A fully meshed communication ability would provide the means for message type 3 (Source Found Message) to be sent directly to an initiating NMS. If a fully meshed communication system is not available, messages may have to traverse multiple systems to reach the initiating NMS as a result of the linear trust relationships established between management systems. Other policy considerations include how the RegistryHandle and NMS IP address should be shared. This should also be coupled with any necessary pre-shared key or certificate (or trusted Security Authority) stored in the NMS for encryption negotiation, where the PKI is a potential solution. Note: The contact information and corresponding IP address for a network RID system would be shared between cooperating networks via a predefined table. This information may be stored locally on RID systems or a central database, X.500, or LDAP server accessible on the secured network used for inter-NP messaging on NMS. The repository would also be used as the border directory to other consortiums for sharing public key information necessary to establish and protect communications. The method of passing the trace request to subsequent networks eliminates the need for granting access to remote entities to configure network equipment on border networks. Access to network equipment to configure systems for trace continuance would remain in the responsibility of the parties who own and manage the equipment. This also prevents the need for sharing authentication information to the devices outside of the network operation center managing the device. Network administrators who have the ability to base the decision on the available resources and other factors of their network maintain control of the continuance of a trace. The ability to dynamically trace packets through packet flow data could be used with malicious intent and reach beyond the intended scope of this protocol. However, if using a valid source address, RID traces would not be necessary since the true source information would already be valid in the packet. Tools such as traceroute can be used to identify path information and/or the relay message could be used for notification purposes to the NP closest to the source to allow for an automated response and action to mitigate the effects of the attack traffic. If tools such as traceroute do not provide the necessary path information in a security incident, the trace request MUST note the system use to avoid instances where the trace is providing information outside Moriarty Expires: August 28, 2004 [Page 48]
Internet-Draft February 28, 2004 the intended and agreed upon scope of the system. 8. Summary Denial of service attacks and other security incidents have always been difficult to trace as a result of the spoofed sources, resource limitations, and bandwidth utilization problems. Incident response is often slow as well even when the valid address is known because of the resources required to notify the responsible party of the attack and then to stop or mitigate the attack traffic. Methods to identify and trace attacks near real time are essential to thwarting attack attempts. Network providers need automated methods as well as policies in place in order to attempt to combat the hacker's efforts. Proactive monitoring and alerting of backbone and client bandwidth with trend analysis and other attack detection techniques need to be integrated into the network to provide automated response capabilities. The automated response capabilities need to identify and trace attacks quickly without resource intensive side effects. Integration with a centralized communication system to coordinate the detection, tracing, and identification of attack sources on a single network are essential. RID provides a way to integrate a network providers resources with their network components for each aspect of detection and identification and extends the communication capabilities where an attack source may have originated on another network. This is accomplished through the flexible IODEF XML based documents that may originate on an IDS system, trigger a network trace, communicate a trace request to an upstream provider and result in an action to stop or mitigate the attack traffic. The messages are communicated between peers using the SOAP protocol and security considerations are provided through existing standards such as the Web Security Model and XML encryption and digital signatures. RID provides the timely communication between NPs, which is essential in incident handling. Moriarty Expires: August 28, 2004 [Page 49]
Internet-Draft February 28, 2004 9. References [ISO 9594/8] CCITT Rec. X.509 (1994) | ISO/IEC 9594-8:1994, Information Technology - Open Systems Interconnection The Directory: Authentication Framework [RFC791] "Internet Protocol, DARPA Internet Program, Protocol Specification". Information Sciences Institute, University of Southern California. September 1981. [RFC1213] "Management Information Base for Network Management of TCP/IP-based Internets: MIB-II". K. McCloghrie, M . Rose. March 1991. [RFC1215] "A Convention for Defining Traps for use with the SNMP". M. Rose. March 1991. [RFC1930] "Guidelines for creation, selection, and registration of an Autonomous System (AS)". J. Hawkinson and T. Bates. March 1996. [RFC2246] "The TLS Protocol". Dierks, T. and C. Allen. January 1999. [RFC2256] "A Summary of the X.500(96) User Schema for use with LDAPv3", Wahl, M., December 1997. [RFC2459] "Internet Public Key Infrastructure: Part I: X.509 Certificate and CRL Profile". Housley, R., Ford, W., Polk, W. and D. Solo. January 1999. [RFC2527] "Internet X.509 Public Key Infrastructure: Certificate Policy and Certification Practices Framework". Chokhani, S., Ford, W. March 1999. [RFC2528] "Internet X.509 Public Key Infrastructure: Representation of Key Exchange Algorithm (KEA) Keys in Internet X.509 Public Key Infrastructure Certificates". Housley, R., Polk, W. March 1999. [RFC2720] "Traffic Flow Measurement: Meter MIB". N. Brownlee. October 1999. [RFC2722]"Traffic Flow Measurement: Architecture". N. Brownlee, C. Mills, G. Ruth. October 1999. [RFC2723] "SRL: A Language for Describing Traffic Flows and Specifying Actions for Flow Groups". N. Brownlee. October 1999. [RFC2827] "Network Ingress Filtering: Defeating Denial of Service Attacks Which Employ IP Source Address Spoofing". P. Ferguson and D. Senie. May 2000. Moriarty Expires: August 28, 2004 [Page 50]
Internet-Draft February 28, 2004 [RFC3821] "An Internet Attribute Certificate Profile for Authorization". Farrell, S., Housley, R. April 2002. [RFCXXXX] ôThe Incident Data Exchange Format Data Model and XML Implementationö. J. Meijer, R. Danyliw, Y. Demchenko. September 2003. http://www.ietf.org/internet-drafts/draft-ietf-inch-iodef-02.txt [1] http://www.info-sec.com/denial/infosece.html-ssi [2] `CenterTrack: An IP Overlay Network for Tracing DoS Floods'. Robert Stone. 9th Usenix Security Symposium Proceedings, August 2000. [3] 'Inferring Internet Denial of Service Activity`. David Moore, Geoffrey M. Voelker and Stephan Savage. Published in proceedings of the 2001 USENIX Security Symposium. [4] 'MULTOPS: A Data-Structure For Bandwidth Attack Detection'. Thomer M. Gil, Massimiliano Poletta. Published in proceedings of the 2001 USENIX Security Symposium. [5] 'Network Congestion Monitoring and Detection using the IMI infrastructure'. Takeo Saitoh, Glenn Mansfield, and Norio Shiratori. Graduate School of Information Sciences, Tohoku University. [6] 'Trends in Denial of Service Attack Technology`. Kevin Houle, George Weaver, Neil Long, and Rob Thomas. CERT Coordination Center. October 2001. [7] http://www.cisco.com/go/netflow [8] 'Hash Based IP Traceback'. A. Snoren, L. Sanchez, C. Jones, F. Tchakountio, S. Kent, and W. Strayer. SIGCOMM'01. August 2001. [9] 'Practical Network support for IP Traceback'. S.Savage, D. Wetherall, A. Karlin and T. Anderson. SIGCOMM'00. August 2000. [10] 'ICMP Traceback Messages'. S. M. Bellovin. Internet Draft: draft-bellovin-itrace-00.txt, March 2000. [11] PKCS 5 v2.0 Password-Based Cryptography Standard. RSA Security http://www.rsasecurity.com/rsalabs/pkcs/pkcs-5/index.html. March 1999. [12] PKCS 7 Cryptographic Message Syntax Standard. RSA Security. http://www.rsasecurity.com/rsalabs/pkcs/pkcs-7/index.html. May 1997. [13] Applied Cryptography: Protocols, Algoritms, and Source Code in C. Schneier, Bruce. Second edition. John Wiley & Sons. 1996. Moriarty Expires: August 28, 2004 [Page 51]
Internet-Draft February 28, 2004 [14] Advanced and Authenticated Marking Schemes for IP Traceback. D. Song and A. Perrig. IEEE INFOCOM 2001. [15] XML Schema. Eric Van der Vlist. OÆReilly. 2002. [16] Extensible Markup Language (XML) 1.0 (Second Edition). W3C Recommendation. T. Bray, E. Maler, J. Paoli, C. M. Sperberg- McQueen. October 2000. http://www.w3.org/TR/2000/REC-xml-20001006 [17] XML-Signature Syntax and Processing. W3C Recommendation. M. Bartel, J. Boyer, B. Fox, B. LaMacchia , E. Simon. February 2002. http://www.w3.org/TR/xmldsig-core/#sec-Design [18] XML Encryption Syntax and Processing, W3C Recommendation. Imamura, T., Dillaway, B. and E. Simon, "", December 2002. http://www.w3.org/TR/xmlenc-core/ [19] Security Architecture for Open Agent Systems. Vrije Universiteit. Y. Demchenko, B. Overiender, H. M. Boonstra. http://carol.science.uva.nl/~demch/worksinprogress/ draft-saas-paper03.pdf [20] ôSecurity in a Web Services World: A Proposed Architecture and Roadmapö. IBM and Microsoft. April 2002. http://www-106.ibm.com/developerworks/webservices/library/ws-secmap Moriarty Expires: August 28, 2004 [Page 52]
Internet-Draft February 28, 2004 9.1 Acknowledgements Dr. Robert K. Cunningham, MIT Lincoln Laboratory Cynthia D. McLain, MIT Lincoln Laboratory Dr. William Streilein, MIT Lincoln Laboratory Many thanks to the Internet community for reviewing and commenting on the draft as well as providing recommendations to simplify and secure the protocol: Iljitsch van Beijnum, Steve Bellovin, Yuri Demchenko, Jean-Francois Morfin, Jose Nazaro, Stephen Northcutt, Jeffrey Schiller, and Tony Tauber. 9.2 Author Information Kathleen M. Moriarty MIT Lincoln Laboratory 244 Wood Street Lexington, MA 02420 Phone: 781-981-5500 Email: Moriarty@ll.mit.edu This work was sponsored by the Air Force under Air Force Contract Number F19628-00-C-0002. "Opinions, interpretations, conclusions, and recommendations are those of the author and are not necessarily endorsed by the United States Government." Moriarty Expires: August 28, 2004 [Page 53]