Network Working Group K. Moriarty
Internet-Draft EMC Corporation
Intended status: Informational A. Morton
Expires: September 8, 2015 AT&T Labs
March 7, 2015
Effect of Encryption
draft-mm-wg-effect-encrypt-00
Abstract
Increased use of encryption will impact operations for security and
network management causing a shift in how these functions are
performed. In some cases, new methods to both monitor and protect
data will evolve. In more drastic circumstances, the ability to
monitor may be eliminated. This draft includes a collection of
current security and network management functions that may be
impacted by the shift to increased use of encryption. This draft
does not attempt to solve these problems, but rather document the
current state to assist in the development of alternate options to
achieve the intended purpose of the documented practices.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
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This Internet-Draft will expire on September 8, 2015.
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Copyright (c) 2015 IETF Trust and the persons identified as the
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Network Service Provider Monitoring . . . . . . . . . . . . . 5
2.1. Middlebox Monitoring . . . . . . . . . . . . . . . . . . 5
2.1.1. Traffic Analysis Fingerprinting . . . . . . . . . . . 5
2.1.2. Traffic Surveys . . . . . . . . . . . . . . . . . . . 6
2.1.3. Deep Packet Inspection (DPI) . . . . . . . . . . . . 6
2.2. Network Monitoring for Performance Management and
Troubleshooting . . . . . . . . . . . . . . . . . . . . . 7
2.3. Inter Data Center Encryption . . . . . . . . . . . . . . 7
2.3.1. new section . . . . . . . . . . . . . . . . . . . . . 7
3. Encryption in Hosting SP Environments . . . . . . . . . . . . 8
3.1. Management Access Security . . . . . . . . . . . . . . . 8
3.1.1. Customer Access Monitoring . . . . . . . . . . . . . 8
3.1.2. Application SP Content Monitoring . . . . . . . . . . 9
3.2. Hosted Applications . . . . . . . . . . . . . . . . . . . 10
3.2.1. Monitoring needs for Managed Applications . . . . . . 10
3.2.2. Mail Service Providers . . . . . . . . . . . . . . . 11
3.2.3. Code Repositories . . . . . . . . . . . . . . . . . . 12
3.2.4. Document Management . . . . . . . . . . . . . . . . . 12
3.3. Data Storage . . . . . . . . . . . . . . . . . . . . . . 12
3.3.1. Host-level Encryption . . . . . . . . . . . . . . . . 12
3.3.2. Disk Encryption, Data at Rest . . . . . . . . . . . . 13
3.3.3. Cross Data Center Replication Services . . . . . . . 14
3.4. new section . . . . . . . . . . . . . . . . . . . . . . . 14
4. Encryption for Enterprise Users . . . . . . . . . . . . . . . 15
4.1. Monitoring Needs of the Enterprise . . . . . . . . . . . 15
4.2. Techniques for Monitoring Internet Session Traffic . . . 16
5. Encryption for Home Users . . . . . . . . . . . . . . . . . . 17
6. Security Monitoring for Specific Attack Types . . . . . . . . 17
6.1. Mail Abuse and SPAM . . . . . . . . . . . . . . . . . . . 17
6.2. Denial of Service . . . . . . . . . . . . . . . . . . . . 18
6.3. Phishing . . . . . . . . . . . . . . . . . . . . . . . . 18
6.4. Botnets . . . . . . . . . . . . . . . . . . . . . . . . . 19
6.5. eCrime . . . . . . . . . . . . . . . . . . . . . . . . . 19
6.6. Malware . . . . . . . . . . . . . . . . . . . . . . . . . 20
6.7. Blocklists . . . . . . . . . . . . . . . . . . . . . . . 20
6.8. [Any other subsections to be contributed?] . . . . . . . 20
7. Response to Increased Encryption and Looking Forward . . . . 20
8. Operational Monitoring . . . . . . . . . . . . . . . . . . . 21
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9. Security Considerations . . . . . . . . . . . . . . . . . . . 21
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 22
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 22
12.1. Normative References . . . . . . . . . . . . . . . . . . 22
12.2. Informative References . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24
1. Introduction
In response to pervasive monitoring revelations and the IETF
consensus that Pervasive Monitoring is an Attack [RFC7258], efforts
are underway to increase encryption of Internet traffic. Session
encryption helps to prevent both passive and active attacks on
transport protocols, with pervasive monitoring being primarily a
passive attack. The Internet Architecture Board (IAB) released a
statement advocating for increased use of encryption in November
2014. Views on acceptable encryption have also shifted and are
documented in "Opportunistic Security" (OS) [RFC7435], where
cleartext sessions should be upgraded to unauthenticated session
encryption, rather than no encryption. OS encourages upgrading from
cleartext, but cannot require or guarantee such upgrades. Once OS is
used, it allows for an upgrade to authenticated encryption. These
efforts are necessary to improve end users expectation of privacy,
making pervasive monitoring cost prohibitive. Active attacks are
still possible on sessions where unauthenticated sessions are in use.
The push for ubiquitous encryption via OS is specific to improving
privacy for everyday users of the Internet. Many attackers and those
that pose a greater threat are already using strong encryption and
tools like TOR [TOR] to prevent active attacks from on their data
streams.
Although there is a push for OS, there is also work being done to
improve implementation development and configuration flaws of TLS and
DTLS sessions to prevent active attacks used to monitor or intercept
session data. The (UTA) working group is in process of publishing
documentation to improve the security of TLS and DTLS sessions. They
have documented the known attack vectors in
[I-D.ietf-uta-tls-attacks] and have documented Best Practices for TLS
and DTLS in [I-D.ietf-uta-tls-bcp].
Current estimates of session encryption approximate that about 30% of
web sites have session encryption enabled, according to the
Electronic Frontier Foundation [EFF]. The Mozilla Foundation
maintains statistics on SSL/TLS usage and as of March 2015, 64% of
HTTP transactions are encrypted. Enterprise networks such as EMC
observe that about 78% of outbound employee traffic was encrypted in
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June 2014. Although the actual number of sites may only be around
30%, they include some of the most visited sites on the Internet for
corporate users.
In addition to encrypted web site access (TLS over HTTP), other
application level transport encryption efforts are underway. This
includes a push to encrypt session transport for mail (SMTP - gateway
to gateway) and other protocols such as instant messaging (TLS over
XMPP). Although this does provide protection from passive
wiretapping [RFC4949] attacks, the servers could be a point of
vulnerability if user-to-user encryption is not provided for these
messaging protocols. User-to-user content encryption schemes, such
as S/MIME and PGP for email and Off-the-Record (OTR) for Extensible
Messaging and Presence Protocol (XMPP) are used by those interested
to protect their data as it crosses intermediary servers, preventing
the vulnerability described by providing an end-to-end solution.
User-to-user schemes are under review and additional options will
emerge to ease the configuration requirements, making this type of
option more accessible to non-technical users interested in
protecting their privacy.
Increased use of encryption (either opportunistic or authenticated)
will impact operations for security and network management causing a
shift in how these functions are performed. In some cases new
methods to monitor and protect data will evolve, for other cases the
need may be eliminated. This draft includes a collection of current
security and network management functions that may be impacted by
this shift to increased use of encryption. This draft does not
attempt to solve these problems, but rather document the current
state to assist in the development of alternate options to achieve
the intended purpose of the documented practices.
In this document we consider several different forms of service
providers, so we distinguish between them with adjectives. For
example, network service providers (or network operators) provide IP-
packet transport primarily, though they may bundle other services
with packet transport. Alternatively, application service providers
primarily offer systems that participate as an end-point in
communications with the application user, and hosting service
providers lease computing, storage, and communications systems in
datacenters. In practice, many companies perform two or more service
provider roles, but may be historically associated with one.
[Contributions are welcome to expand the list of documented
practices]
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2. Network Service Provider Monitoring
Network Service Providers (SP) are responding to encryption on the
Internet, some helping to increase the use of encryption and others
preventing its use. Network SPs for this definition include the
backbone Internet Service providers as well as those providing
infrastructure at scale for core Internet use (hosted infrastructure
and services such as email).
Following the Snowden revelations, application service providers
responded by encrypting traffic between their data centers to prevent
passive monitoring from taking place unbeknownst to the providers
(Yahoo, Google, etc.). Large mail service providers also began to
encrypt session transport to hosted mail services. This had an
immediate impact to help protect the privacy of users data, but
created a problem for network operators. They could no longer gain
access to session streams resulting in actions by several to regain
their operational practices that require cleartext data sessions.
The EFF reported several network service providers taking steps to
prevent the use of TLS over SMTP by breaking StartTLS, preventing the
negotiation process resulting in fallback to the use of clear text.
The use of encryption prevents middle boxes from performing functions
that range from load balancing to monitoring for attacks or enabling
"lawful intercept" in the US [CALEA]. Some of these practices may be
on the decline now that they are exposed through the media, but they
are representative of the struggles administrators will have with
changes in their ability to monitor and manage traffic.
2.1. Middlebox Monitoring
Network service providers use various monitoring techniques for
security and operational purposes. The following subsections detail
the purpose of each type of monitoring and what protocol fields are
used to accomplish the task.
2.1.1. Traffic Analysis Fingerprinting
Fingerprinting is used in traffic analysis and monitoring to identify
traffic streams that match certain patterns. This technique may be
used with clear text or encrypted sessions. Some Distributed Denial
of Service (DDoS) prevention techniques at the Network SP level rely
on the ability to fingerprint traffic in order to mitigate the effect
of this type of attack. Thus, fingerprinting may be an aspect of an
attack or part of attack countermeasures.
The first/obvious trigger for DDoS mitigation is uncharacteristic
traffic volume and/or congestion at various points associated with
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the attackee's communications. One approach to mitigate such an
attack involves distinguishing attacker traffic from legitimate user
traffic through analysis. The ability to examine layers and payloads
above transport provides a new range of filtering opportunities at
each layer in the clear. Fewer layers are in the clear means reduced
filtering opportunities to mitigate attacks.
Traffic analysis fingerprinting could also be used on web traffic to
perform passive monitoring and invade privacy.
For example, browser fingerprints are comprised of many
characteristics, including User Agent, HTTP Accept headers, browser
plug-in details, screen size and color details, system fonts and time
zone. [PANO] will audit these details for users. A monitoring
system could easily identify a specific browser, and by correlating
other information, identify a specific user.
2.1.2. Traffic Surveys
Internet traffic surveys are useful in many well-intentioned
pursuits, such as CAIDA data [CAIDA] and SP network design and
optimization. Tracking the trends in Internet traffic growth, from
earlier peer-to-peer communication to the extensive adoption of
unicast video streaming applications, has required a view of traffic
composition and reports with acceptable accuracy. As application
designers and network operators both continue to seek optimizations,
the role of traffic surveys from passive monitoring grows in
importance.
Passive monitoring makes inferences about observed traffic using the
maximal information available, and is subject to inaccuracies
stemming from incomplete sampling (of packets in a stream) or loss
due to monitoring system overload. When encryption conceals more
layers in each packet, reliance on pattern inferences and other
heuristics grows, and accuracy suffers. For example, the traffic
patterns between server and browser are dependent on browser supplier
and version, even when the sessions use the same server application
(e.g., web e-mail access). It remains to be seen whether more
complex inferences can be mastered to produce the same monitoring
accuracy.
2.1.3. Deep Packet Inspection (DPI)
The features and efficiency of some Internet services can be
augmented through analysis of user flows and the applications they
provide. For example, network caching of popular content at a
location close to the requesting user can improve delivery
efficiency, and authorized parties use DPI in combination with
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content distribution networks to determine if they can intervene
effectively. Encryption of packet contents at a given protocol layer
usually makes inspection of that layer and higher layers impossible,
as well as DPI processing at the formerly clear text layers.
2.2. Network Monitoring for Performance Management and Troubleshooting
Similar to DPI, the performance of some services can be more
efficiently managed and repaired when information on user
transactions is available to the service provider. It may be
possible to continue such monitoring activities without clear text
access to the application layers of interest, but inaccuracy will
increase and efficiency of repair activities will decrease. Also,
there may be more cases of user communication failures when the
additional encryption processes are introduced, leading to more
customer service contacts and (at the same time) less information
available to network operations repair teams.
[Types of network and performance monitoring used by IP-level service
providers should be discussed here. How does encryption impact their
current techniques? What do they use in data streams to maintain
expected service levels?]
With the growing use of WebSockets [RFC6455], many forms of
communications (from isochronous/real-time to bulk/elastic file
transfer) will take place over HTTP port 80, so only the messages and
higher-layer data will make application differentiation possible. If
the monitoring systems sees only "HTTP port 443", it cannot
distinguish application streams that would benefit from priority
queueing from others that would not. In short, systems that invoked
policies for the user's benefit are rendered less-effective (or in-
effective) by encryption of information they once viewed easily.
2.3. Inter Data Center Encryption
The use of encryption at an IP-level between data centers of large
application service providers has increased as a result of
revelations that governments were passively monitoring these
connections. [How has security and operations monitoring of these
session been impacted or has that been fully addressed and how?
Storage section contains one example that fits this scenario.]
2.3.1. new section
[Needs for monitoring from an operational perspective could be in
subsections to this bullet, contributions welcome to understand and
document the struggle to determine alternate approaches in subsequent
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efforts. This should include specific monitoring goals as well as
what is currently used to achieve those goals - how and why.]
3. Encryption in Hosting SP Environments
Hosted environments have had varied requirements in the past for
encryption, with many businesses choosing to use these services
primarily for data and applications that are not business or privacy
sensitive. A shift prior to the revelations on surveillance/passive
monitoring began where businesses were asking for hosted environments
to provide higher levels of security so that additional applications
and service could be hosted externally. Businesses understanding the
threats of monitoring in hosted environments only increased that
pressure to provide more secure access and session encryption to
protect the management of hosted environments as well as for the data
and applications.
3.1. Management Access Security
Hosted environments may have multiple levels of management access,
where some may be strictly for the Hosting SP (infrastructure that
may be shared among customers) and some may be accessed by a specific
customer for application management. In some cases, there are
multiple levels of hosting service providers, further complicating
the security of management infrastructure and the associated
requirements.
Hosting service provider management access is typically segregated
from other traffic with a control channel and may or may not be
encrypted depending upon the isolation characteristics of the
management session. Customer access may be through a dedicated
connection, but this is becoming less common with newer hosted
service models leveraging the Internet.
3.1.1. Customer Access Monitoring
Hosted applications that allow some level of customer management
access may also require monitoring by the hosting service provider.
The monitoring needs could include access control restrictions such
as authentication, authorization, and accounting for filtering and
firewall rules to ensure they are continuously met. Customer access
may occur on multiple levels, including user-level and administrative
access. The hosting service provider may need to monitor access
either through session monitoring or log evaluation to ensure
security service level agreements (SLA) for access management are
met. The use of session encryption to access hosted environments
will limit the ability to use session data to ensure access
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restrictions are maintained. Monitoring and filtering may occur at
an:
2-tuple IP-level with source and destination IP addresses alone, or
5-tuple IP and protocol-level with source IP address, destination IP
address, protocol number, source port number, and destination port
number.
Session encryption at the application level, TLS for example,
currently allows access to the 5-tuple. IP-level encryption, such as
IPsec in tunnel mode prevents access to the 5-tuple and may limit the
ability to restrict traffic via filtering techniques. This shift may
not impact all hosting service provider solutions as alternate
controls may be used to authenticate sessions or access may require
that mobile clients access such services by first connecting to the
organization before accessing the hosted application. Shifts in
access may be required to maintain equivalent access control
management. Logs may also be used for monitoring access control
restrictions are met, but would be limited to the data that could be
observed due to encryption at the point of log generation. Log
analysis is out of scope for this document.
Intrusion detection, performance, availability, [What else should be
covered in this section?]
3.1.2. Application SP Content Monitoring
Application Service Providers may offer content-level monitoring
options to detect intellectual property leakage, or other attacks.
The use of session encryption will prevent Data Leakage Protection
(DLP) used on the session streams from accessing content to search on
keywords or phases to detect such leakage. DLP is often used to
prevent the leakage of Personally Identifiable Information (PII) as
well as financial account information, Personal Health Information
(PHI), and Payment Card Information (PCI). If session encryption is
terminated at a gateway prior to accessing these services, DLP on
session data can still be performed. The decision of where to
terminate encryption to hosted environments will be a risk decision
made between the application service provider and customer
organization according to their priorities. DLP can be performed at
the server for the hosted application and on an end users system in
an organization as alternate or additional monitoring points of
content, however is not frequently done in a service provider
environment.
[What other monitoring is specific to SP Applications? This likely
includes monitoring equipment, change control processing,
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configuration monitoring, security control compliance, performance,
availability, OAM, etc. A number of the possibilities within these
brackets may occur within the SP environment and may or may not be
impacted by the push for encryption. With increasingly security
applications moving to hosted environments, tenant isolation may
require use of encryption inside of the data center. Should we
discuss that here so the impact is understood and what monitoring
performed today is documented?]
3.2. Hosted Applications
Organizations are increasingly using hosted applications rather than
in house solutions that require maintenance of equipment and
software. Examples include Enterprise Resource Planning (ERP)
solutions, payroll service, time and attendance, travel and expense
reporting among others. Organizations may require some level of
management access to these hosted applications and will typically
require session encryption or a dedicated channel for this activity.
In other cases, hosted applications may be fully managed by a hosting
service provider with service level agreement expectations for
availability and performance as well as for security functions
including malware detection.
3.2.1. Monitoring needs for Managed Applications
Performance, availability, and other SLA requirements, etc. [What
monitoring is done by these SPs, why, and what do they monitor? Can
this section cover the operational aspect for each of the offerings
listed below, or do they need to be broken out by service?]
Performance, availability, and other aspects of a SLA are often
collected through passive monitoring. For example:
o Availability: ability to establish connections with hosts to
access applications, and discern the difference between network or
host-related causes of unavailability.
o Performance: ability to complete transactions within a target
response time, and discern the difference between network or host-
related causes of excess response time.
Here, as with all passive monitoring, the accuracy of inferences are
dependent on the cleartext information available, and encryption
would tend to reduce the information and therefore, the accuracy.
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3.2.2. Mail Service Providers
Mail (application) service providers vary in what services they
offer. Options may include a fully hosted solution where mail is
stored external to an organization's environment on mail service
provider equipment or the service offering may be limited to monitor
incoming mail to remove SPAM [Section 6.1], malware [Section 6.6],
and phishing attacks [Section 6.3] before mail is directed to the
organization's equipment. In both of these cases, content of the
messages and headers is monitored to detect SPAM, malware, phishing,
and other messages that may be considered an attack.
In addition to the monitoring needs for specific attack types
discussed in Section 6, mail service providers [Need descriptions for
other types of monitoring performed. What is used now in their
monitoring? How will use of TLS between servers impact their ability
to monitor for security or operations? Users have no idea if the TLS
covers their entire session stream or if it's left in clear text over
some of the hops in this hop-by-hop protection - does this matter and
how does it impact monitoring or do monitoring needs lead to this
problem (broken STARTTLS negotiations)?
Many efforts are emerging to improve user-to-user encryption to
protect end user's privacy. Some of these efforts involve encryption
of email header information such as the message subject. Mail system
operators could still find enough helpful information in the rest of
the header fields if the subject was no longer accessible, however it
could reduce effectiveness of administrators. In some cases,
administrators may search on mail systems for known subject fields of
abuse messages from inboxes or mail queues to remove phishing or
other messages that contain malware or links to malware. Their
ability to perform prevention may be more limited with full
deployment of end-to-end mail encryption with header fields
inaccessible. The header fields [RFC2822] used most often in their
operational work include:
o Subject: - may be considered privacy sensitive
o To:/From: - may be considered privacy sensitive
o Received: from
o Date:
o Sent:
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3.2.3. Code Repositories
Intrusion detection, performance, availability, malware detection,
etc. [What monitoring is done by these SPs, why, and what do they
monitor?]
3.2.4. Document Management
Intrusion detection, performance, availability, malware detection,
etc. [What monitoring is done by these SPs, why, and what do they
monitor?]
3.3. Data Storage
Numerous service offerings exist that provide hosted storage
solutions. This section describes the various offerings and details
the monitoring for each type of service and how encryption may impact
the operational and security monitoring performed.
Trends in data storage encryption for hosted environments include a
range of options. The following list is intentionally high-level to
describe the types of encryption used in coordination with data
storage that may be hosted remotely, meaning the storage is
physically located in an external data center requiring transport
over the Internet. Options for monitoring will vary with both
approaches from what may be done today.
3.3.1. Host-level Encryption
For higher security and/or privacy of data and applications, options
that provide end-to-end encryption of the data from the users desktop
or server to the storage platform may be preferred. With this
description, host level encryption includes any solution that
encrypts data at the object level, not transport. Encryption of data
may be performed with libraries on the system or at the application
level, which includes file encryption services via a file manager.
Host-level encryption is useful when data storage is hosted or when
in scenarios when storage location is determined based on capacity or
based on a set of parameters to automate decisions. This could mean
that large data sets accessed infrequently could be sent to an off-
site storage platform at an external hosting service, data accessed
frequently may be stored locally, or decision could be based on the
transaction type. Host-level encryption is grouped separately for
the purpose of this document as the monitoring needs as this data is
bursted to off-site storage platforms, where traffic crosses the
Internet are similar. If session encryption is used, the protocol is
likely to be TLS.
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3.3.1.1. Monitoring for Hosted Storage
The general monitoring needs of hosted storage solutions that use
host-level (object) encryption is described in this subsection.
Solutions might include backup services and external storage
services, such as those that burst data that exceeds internal limits
on occasion to external storage platforms operated by a third party.
Monitoring of data flows to hosted storage solutions is performed for
security and operational purposes. The security monitoring may be to
detect anomalies in the data flows that could include changes to
destination, the amount of data transferred, or alterations in the
size and frequency of flows. Operational considerations include
capacity and availability monitoring.
[What is monitored in the flows? What data is monitored when the
sessions are encrypted vs. when session encryption is not in use?
Note that object encryption may not be used in all cases.]
3.3.1.1.1. Backup Storage
[This is a placeholder in case there are distinct monitoring needs
for any of the options that fall into this category. Backup Storage
is listed as an example, but will be removed if there are no
monitoring needs that needs to be discussed at a more granular level
than the general description.]
3.3.2. Disk Encryption, Data at Rest
There are multiple ways to achieve full disk encryption for stored
data. Encryption may be performed on data to be stored while in
transit close to the storage media with solutions like Controller
Based Encryption (CBE) or in the drive system with Self-Encrypting
Drives (SED). Session encryption is typically coupled with
encryption of these data at rest (DAR) solutions to also protect data
in transit. Transport encryption is likely via TLS.
3.3.2.1. Monitoring Session Flows for DAR Solutions
The general monitoring needs for transport of data to storage
platforms, where object level encryption is performed close to or on
the storage platform are similar to those described in the section on
Monitoring for Hosted Storage. The primary difference for these
solutions is the possible exposure of sensitive information, which
could include privacy related data, financial information, or
intellectual property if session encryption via TLS is not deployed.
Session encryption is typically used with these solutions, but that
decision would be based on a risk assessment. There are use cases
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where DAR or disk-level encryption is required. Examples include
preventing exposure of data if physical disks are stolen or lost as
data is decrypted upon access when that access is from the expected
and configured application or service.
[What is monitored in the flows? What data is monitored when the
sessions are encrypted vs. when session encryption is not in use?
There is obvious exposure of data when session encryption is not in
use and session monitoring is not necessarily limited to the 5-tuple.
Contributions welcome from those that have knowledge of what is
actually used in monitoring of these sessions.]
3.3.3. Cross Data Center Replication Services
Storage services also include data replication which may occur
between data centers and may leverage Internet connections to tunnel
traffic. The traffic may use iSCSI [RFC7143] or FC/IP [RFC7146]
encapsulated in IPsec. Either transport or tunnel mode may be used
for IPsec depending upon the termination points of the IPsec session,
if it is from the storage platform itself or from a gateway device at
the edge of the data center respectively.
3.3.3.1. Monitoring Of IPSec for Data Replication Services
The general monitoring needs for data replication are described in
this subsection.
Monitoring of data flows between data centers may be performed for
security and operational purposes and would typically concentrate
more on the operational needs since these flows are essentially
virtual private networks (VPN) between data centers. Operational
considerations include capacity and availability monitoring
[Contributions to expand this description and the more detailed data
used for analysis below is welcome.]. The security monitoring may be
to detect anomalies in the data flows, similar to what was described
in the "Monitoring for Hosted Storage Section".
[What is monitored in the flows? What data is monitored when the
sessions are encrypted vs. when session encryption is not in use?
Note that object encryption may not be used in all cases.]
3.4. new section
[Did we miss anything that should go here?]
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4. Encryption for Enterprise Users
This section is limited to the use of encryption by enterprise users
to the Internet and not that of internal enterprise networks. To
date, there is not yet demand to encrypt internal networks, with the
exception of sensitive data and applications and those that require
encryption through regulatory requirements.
4.1. Monitoring Needs of the Enterprise
Enterprise users are subject to the policies of their organization.
As such, proxies may be in use to:
1. intercept outbound session traffic to monitor for intellectual
property leakage (by users or more likely these days through
malware and trojans),
2. detect viruses/malware entering the network via email or web
traffic,
3. detect malware/Trojans in action, possibly connecting to remote
hosts,
4. detect attacks (Cross site scripting and other common web related
attacks),
5. track misuse and abuse by employees,
6. restrict the types of protocols permitted to/from the corporate
environment,
7. assess traffic volume on a per-application basis, for billing,
capacity planning, optimization of geographical location for
servers or proxies, and other needs,
8. assess performance in terms of application response time and user
perceived response time, and
9. re-direct to requests to caches of popular or bandwidth-intensive
Internet content.
For each type of monitoring, different techniques and parts of the
data stream may be necessary. As we transition to an increased use
of encryption that is increasingly harder to break, alternate methods
of monitoring for operational purposes will be necessary to prevent
the need to break encryption and thus privacy of users (which may not
apply in a corporate setting by policy).
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4.2. Techniques for Monitoring Internet Session Traffic
Corporate networks commonly monitor outbound session traffic to
detect or prevent attacks as well as to guarantee service level
expectations. In some cases, alternate options are available when
encryption is in use, but techniques like that of data leakage
prevention tools at a proxy would not be possible if encrypted
traffic can not be intercepted, thus requiring alternate options to
emerge.
Data leakage detection prevention (DLP) tools intercept traffic at
the Internet gateway or proxy services with the ability to man-in-
the-middle (MiTM) encrypted session traffic (HTTP/TLS). These tools
may use key words important to the enterprise including business
sensitive information such as trade secrets, financial data,
personally identifiable information (PII), or personal health
information (PHI). Various techniques are used to intercept HTTP/TLS
sessions for DLP and other purposes, and are described in
"Summarizing Known Attacks on TLS and DTLS"
[I-D.ietf-uta-tls-attacks]. Note: many corporate policies allow
access to personal financial and other sites for users without
interception.
Monitoring traffic patterns for anomalous behavior such as increased
flows of traffic that could be bursty at odd times or flows to
unusual destinations (small or large amounts of traffic). This
traffic may or may not be encrypted and various methods of encryption
or just obfuscation may be used.
Restrictions on traffic to approved sites: Web proxies are sometimes
used to filter traffic, allowing only access to well-known sites
known to be legitimate and free of malware on last check by a proxy
service company. This type of restriction is usually not noticeable
in a corporate setting, but may be to those in research who could
access colleagues individual sites or new web sites that have not yet
been screened. In situations where new sites are required for
access, they can typically be added after notification by the user or
proxy log alerts and review. Home mail account access may be blocked
in corporate settings to prevent another vector for malware to enter
as well as for intellectual property to leak out of the network.
This method remains functional with increased use of encryption and
may be more effective at preventing malware from entering the
network. Web proxy solutions monitor and potentially restrict access
based on the destination URL or the DNS name. A complete URL may be
used in cases where access restrictions vary for content on a
particular site or for the sites hosted on a particular server.
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Desktop DLP tools are used in some corporate environments as well.
Since these tools reside on the desktop, they can intercept traffic
before it is encrypted and may provide a continued method of
monitoring intellectual property leakage from the desktop to the
Internet or attached devices.
DLP tools can also be deployed by Network Service providers, as they
have the unique and efficient vantage point of monitoring all traffic
paired with destinations off the enterprise network. This makes an
effective solution for enterprises that allow "bring-you-own" devices
and devices that do not fit the desktop category, but are used on
corporate networks nonetheless.
Enterprises may wish to reduce the traffic on their Internet access
facilities by monitoring requests for within-policy content and
caching it. In this case, repeated requests for Internet content
spawned by URLs in e-mail trade newsletters or other sources can be
served within the enterprise network. Gradual deployment of end to
end encryption would tend to reduce the cacheable content over time,
owing to concealment of critical headers and payloads. Many forms of
enterprise performance management and optimization based on
monitoring (DPI) would suffer the same fate.
5. Encryption for Home Users
[text]
6. Security Monitoring for Specific Attack Types
Effective incident response today requires collaboration at Internet
scale. This section will only focus on efforts of collaboration at
Internet scale that are dedicated to specific attack types. They may
require new monitoring and detection techniques in an increasingly
encrypted Internet. As mentioned previously, some service providers
have been interfering with STARTTLS to prevent session encryption to
be able to perform functions they are used to (injecting ads,
monitoring, etc.). By detailing the current monitoring methods used
for attack detection and response, this information can be used to
devise new monitoring methods that will be effective in the changed
Internet via collaboration and innovation.
6.1. Mail Abuse and SPAM
The largest operational effort to prevent mail abuse is through the
Messaging, Malware, Mobile Anti-Abuse Working Group (M3AAWG)[M3AAWG].
Mail abuse is combated directly with mail administrators who can shut
down or stop continued mail abuse originating from large scale
providers that participate in using the Abuse Reporting Format (ARF)
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agents standardized in the IETF [RFC5965], [RFC6430], [RFC6590],
[RFC6591], [RFC6650], [RFC6651], and [RFC6652]. The ARF agent
directly reports abuse messages to the appropriate service provider
who can take action to stop or mitigate the abuse. Since this
technique uses the actual message, the use of TLS over SMTP between
mail gateways will not effect its usefulness. As mentioned
previously, TLS over SMTP only protects data while in transit and the
messages may be exposed on mail servers or mail gateways if a user-
to-user encryption method is not used. Current user-to-user message
encryption methods on email (S/MIME and PGP) do not encrypt the email
header information used by ARF and the service provider operators in
their abuse mitigation efforts.
6.2. Denial of Service
Response to Denial of Service (DoS) attacks are typically coordinated
by the SP community with a few key vendors who have tools to assist
in the mitigation efforts. Traffic patterns are determined from each
DoS attack to stop or rate limit the traffic flows with patterns
unique to that DoS attack.
Data types used in monitoring traffic for DDoS are described in Open
Threat Signaling using RPC API over HTTPS and IPFIX (DDoSMitigation:
[I-D.teague-open-threat-signaling]).
Data types used in DDoS attacks have been detailed in the IODEF
Guidance draft [I-D.ietf-mile-iodef-guidance], Appendix A.2, with the
help of several members of the service provider community. The
examples provided are intended to help identify the useful data in
detecting and mitigating these attacks independent of the transport
and protocol descriptions in the drafts. [We don't care about a
format battle for the purpose of this draft, just what is useful for
monitoring.]
[several experts in this area participate in the IETF. It would be
good to get an up-to-date picture of this and what information is
typically helpful in those flows.]
[If sessions are encrypted, how does that affect the ability of SPs
and vendors to mitigate or stop the DoS? ACM: a short description of
the effect appears in section 2]
6.3. Phishing
Investigations and response to phishing attacks follow well-known
patterns, requiring access to specific fields in email headers as
well as content from the body of the message. When reporting
phishing attacks, the recipient has access to each field as well as
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the body to make content reporting possible, even when end-to-end
encryption is used. The email header information is useful to
identify the mail servers and accounts used to generate or relay the
attack messages in order to take the appropriate actions. The
content of the message often contains an embedded attack that may be
in an infected file or may be a link that results in the download of
malware to the users system.
Administrators often find it helpful to use header information to
track down similar message in their mail queue or users inboxes to
prevent further infection. Combinations of To:, From:, Subject:,
Received: from header information might be used for this purpose.
Administrators may also search for document attachments of the same
name, size, or containing a file with a matching hash to a known
phishing attack. Administrators might also add URLs contained in
messages to block lists locally or this may also be done by browser
vendors through larger scales efforts like that of the Anti-Phishing
Working Group (APWG).
A full list of the fields used in phishing attack incident response
can be found in RFC5901. Future plans to increase privacy
protections may limit some of these capabilities if some email header
fields are encrypted, such as To:, From:, and Subject: header fields.
This does not mean that those fields should not be encrypted, only
that we should be aware of how they are currently used. Alternate
options to detect and prevent phishing attacks may be needed. More
recent examples of data exchanged in spear phishing attacks has been
detailed in the IODEF Guidance draft [I-D.ietf-mile-iodef-guidance],
Appendix A.3.
6.4. Botnets
Botnet detection and mitigation is complex and may involve hundreds
or thousands of hosts with numerous Command and Control (C&C)
servers. The techniques and data used to monitor and detect each may
vary. Connections to C&C servers are typically encrypted, therefore
a move to an increasingly encrypted Internet may not affect the
detection and sharing methods used.
[Contributions welcome to detail data used in Botnet detection and
how that may change in an increasingly encrypted Internet.]
6.5. eCrime
[Contributions welcome to better understand data used in tracking
eCrime and how that may change in an increasingly encrypted
Internet.]
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6.6. Malware
Malware monitoring and detection techniques vary. As mentioned in
the enterprise section, malware monitoring may occur at gateways to
the organization analyzing email and web traffic. These services can
also be provided by service providers, changing the scale and
location of this type of monitoring. Additionally, incident
responders may identify attributes unique to types of malware to help
track down instances by their communication patterns on the Internet
or by alterations to hosts and servers.
[Contributions welcome to expand this (or any other) section.] Data
types used in malware investigations have been summarized in an
example of the IODEF Guidance draft [I-D.ietf-mile-iodef-guidance],
Appendix A.1.
6.7. Blocklists
6.8. [Any other subsections to be contributed?]
Although incident response work will continue, new methods to prevent
system compromise through security automation and continuous
monitoring [SACM] may provide alternate approaches where system
security is maintained as a preventative measure.
7. Response to Increased Encryption and Looking Forward
As the use of encryption continues to increase, efforts to prevent it
will continue to emerge. In the best case scenario, engineers and
other innovators would work to solve the problems at hand in new ways
rather than prevent the use of encryption. It will take time to
devise alternate approaches to achieve similar goals.
There has already been documented cases of service providers
preventing STARTTLS [NoEncrypt] to prevent session encryption
negotiation on some session to inject a super cookie. There are
other service providers who have been injecting Java Script into
sessions [Net-Neutral], which has obvious security implications as
well as threatens Net-Neutrality. The use of session encryption will
help to prevent possible discrimination to maintain net neutrality,
but a backlash should be expected.
National surveillance programs have a clear need for monitoring
terrorism [CharlieHebdo] as do Internet security practitioners for
cyber criminal activities. The UK prime minister, David Cameron,
emphasized the need for monitoring [UKMonitor] at the expense of user
privacy and protection of data and assets. This approach ignores the
real need to protect users identity, financial transactions and
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intellectual property, which requires security and encryption to
prevent cyber crime. A clear understanding of technology,
encryption, and monitoring needs will aid in the development of
solutions to appropriately balance the need of privacy and avoid the
fears of terrorism. As this understanding increases, hopefully the
discussions will improve and this draft is meant to help further the
discussion.
Terrorists and cyber criminals have been using encryption for many
years. The current push to increase encryption is aimed at
increasing users privacy. There is already protection in place for
purchases, financial transactions, systems management infrastructure,
and intellectual property although this too can be improved. The
Opportunistic Security (OS) [RFC7435] efforts aim to increase the
costs of monitoring through the use of encryption that can be subject
to active attacks, but make passive monitoring broadly cost
prohibitive. This is meant to restrict monitoring to sessions where
there is reason to have suspicion.
As the use of encryption increases, does passive monitoring become
limited to metadata analysis? What metadata should be left in
protocols as they evolve to also protect users privacy? Can we make
changes to protocols and message exchanges to alter the current
monitoring needs at least for operations and security practitioners?
Options are on the technology horizon that will help to end the
struggle between the need to monitor by operators, security teams,
and nations and those seeking to protect users privacy. The
solutions are very interesting, but are several years out and include
homomorphic encrypt, functional encryption, and filterable decryption
[homomorphic]. This technology will allow for searching and pattern
matching on encrypted data, but is still several years out.
8. Operational Monitoring
9. Security Considerations
There are no additional security considerations as this is a summary
and does not include a new protocol or functionality.
10. IANA Considerations
This memo makes no requests of IANA.
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11. Acknowledgements
Thanks to our early reviewers, Ashutosh Dutta and Brandon Williams,
for their editorial and content suggestions.
12. References
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4949] Shirey, R., "Internet Security Glossary, Version 2", RFC
4949, August 2007.
12.2. Informative References
[CAIDA] "CAIDA [http://www.caida.org/data/overview/]", .
[CALEA] Pub. L. No. 103-414, 108 Stat. 4279, codified at 47 USC
1001-1010, "Communications Assistance for Law Enforcement
Act (CALEA)", .
[CharlieHebdo]
"Europe Considers Surveillance Expansion After Deady
Attacks https://firstlook.org/theintercept/2015/01/20/
europe-considers-surveillance-expansion/", .
[EFF] "Electronic Frontier Foundation https://www.eff.org/", .
[I-D.ietf-mile-iodef-guidance]
Kampanakis, P., "IODEF Usage Guidance", draft-ietf-mile-
iodef-guidance-03 (work in progress), May 2014.
[I-D.ietf-uta-tls-attacks]
Sheffer, Y., Holz, R., and P. Saint-Andre, "Summarizing
Known Attacks on TLS and DTLS", draft-ietf-uta-tls-
attacks-05 (work in progress), October 2014.
[I-D.ietf-uta-tls-bcp]
Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of TLS and DTLS", draft-
ietf-uta-tls-bcp-11 (work in progress), February 2015.
[I-D.teague-open-threat-signaling]
Teague, N., "Open Threat Signaling using RPC API over
HTTPS and IPFIX", draft-teague-open-threat-signaling-00
(work in progress), January 2015.
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[M3AAWG] "Messaging, Malware, Mobile Anti-Abuse Working Group
(M3AAWG) https://www.maawg.org/", .
[Net-Neutral]
"Comcast Wifi serving self-promotional ads via JavaScript
injection http://arstechnica.com/tech-policy/2014/09/why-
comcasts-javascript-ad-injections-threaten-security-net-
neutrality/", .
[NoEncrypt]
"ISPs Removing their Customers EMail Encryption
https://www.eff.org/deeplinks/2014/11/starttls-downgrade-
attacks/", .
[PANO] "Panopticlick [https://panopticlick.eff.org/]", .
[RFC2822] Resnick, P., "Internet Message Format", RFC 2822, April
2001.
[RFC5965] Shafranovich, Y., Levine, J., and M. Kucherawy, "An
Extensible Format for Email Feedback Reports", RFC 5965,
August 2010.
[RFC6430] Li, K. and B. Leiba, "Email Feedback Report Type Value:
not-spam", RFC 6430, November 2011.
[RFC6455] Fette, I. and A. Melnikov, "The WebSocket Protocol", RFC
6455, December 2011.
[RFC6590] Falk, J. and M. Kucherawy, "Redaction of Potentially
Sensitive Data from Mail Abuse Reports", RFC 6590, April
2012.
[RFC6591] Fontana, H., "Authentication Failure Reporting Using the
Abuse Reporting Format", RFC 6591, April 2012.
[RFC6650] Falk, J. and M. Kucherawy, "Creation and Use of Email
Feedback Reports: An Applicability Statement for the Abuse
Reporting Format (ARF)", RFC 6650, June 2012.
[RFC6651] Kucherawy, M., "Extensions to DomainKeys Identified Mail
(DKIM) for Failure Reporting", RFC 6651, June 2012.
[RFC6652] Kitterman, S., "Sender Policy Framework (SPF)
Authentication Failure Reporting Using the Abuse Reporting
Format", RFC 6652, June 2012.
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[RFC7143] Chadalapaka, M., Satran, J., Meth, K., and D. Black,
"Internet Small Computer System Interface (iSCSI) Protocol
(Consolidated)", RFC 7143, April 2014.
[RFC7146] Black, D. and P. Koning, "Securing Block Storage Protocols
over IP: RFC 3723 Requirements Update for IPsec v3", RFC
7146, April 2014.
[RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
Attack", BCP 188, RFC 7258, May 2014.
[RFC7435] Dukhovni, V., "Opportunistic Security: Some Protection
Most of the Time", RFC 7435, December 2014.
[TOR] "TOR ...", .
[UKMonitor]
"Cameron wants to ban encryption
http://www.theguardian.com/commentisfree/2015/jan/13/
cameron-ban-encryption-digital-britain-online-shopping-
banking-messaging-terror", .
[homomorphic]
"Securing the Cloud http://newsoffice.mit.edu/2013/
algorithm-solves-homomorphic-encryption-problem-0610", .
Authors' Addresses
Kathleen Moriarty
EMC Corporation
176 South St
Hopkinton, MA
USA
Phone: +1
Email: Kathleen.Moriarty@emc.com
Al Morton
AT&T Labs
200 Laurel Avenue South
Middletown,, NJ 07748
USA
Phone: +1 732 420 1571
Fax: +1 732 368 1192
Email: acmorton@att.com
URI: http://home.comcast.net/~acmacm/
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