OPSEC                                                            P. Cain
Internet-Draft                               The Cooper-Cain Group, Inc.
Intended status: Informational                                  G. Jones
Expires: September 2, 2007                                 March 1, 2007


           Logging Capabilities for IP Network Infrastructure
                    draft-ietf-opsec-logging-caps-02

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Copyright Notice

   Copyright (C) The IETF Trust (2007).














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Abstract

   This document lists logging capabilities originally defined in
   RFC3871 [RFC3871] and needed to support current operational
   practices, including those described in the Operational Security
   Current Practices document[RFC4778] Logging is defined as the
   delivery of messages about the device, the data passing through the
   device, or the device's interaction with another device.  This
   document may be used in conjunction with the other capabilities
   documents to operate a secure networking environment.

   Capabilities are defined without reference to specific technologies.
   This is done to leave room for deployment of new technologies that
   implement the capability.  Each capability cites the practices it
   supports.  Current implementations that support the capability are
   cited.  Special considerations are discussed as appropriate listing
   operational and resource constraints, limitations of current
   implementations, trade-offs, etc.

































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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Security Overview  . . . . . . . . . . . . . . . . . . . .  4
     1.2.  Capabilities vs. Requirements  . . . . . . . . . . . . . .  5
     1.3.  Format . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   2.  Functional Capabilities of Log Generating Systems  . . . . . .  6
     2.1.  Logging Facility Uses Protocols Subject To Open Review . .  6
     2.2.  Logs Sent To Remote Servers  . . . . . . . . . . . . . . .  7
     2.3.  Ability to Select Reliable Delivery  . . . . . . . . . . .  8
     2.4.  Ability to Remotely Log Securely . . . . . . . . . . . . .  9
     2.5.  Ability to Log Locally . . . . . . . . . . . . . . . . . . 10
     2.6.  Ability to Log Different Severities to Different
           Destinations . . . . . . . . . . . . . . . . . . . . . . . 11
     2.7.  Ability to Log to Multiple Destinations  . . . . . . . . . 11
     2.8.  Ability to Maintain Accurate System Time . . . . . . . . . 12
     2.9.  Display Timezone and UTC Offset  . . . . . . . . . . . . . 13
     2.10. Default Timezone Should Be UTC . . . . . . . . . . . . . . 14
     2.11. Log Entries Must Be Timestamped  . . . . . . . . . . . . . 15
     2.12. Log on Exception or Identified Event . . . . . . . . . . . 15
     2.13. Logs Contain Untranslated IP Addresses . . . . . . . . . . 16
     2.14. Logs Contain Records Of Critical Security Events . . . . . 17
     2.15. Logs Contain Records of General Security Events  . . . . . 18
     2.16. Logs Do Not Contain Passwords  . . . . . . . . . . . . . . 19
     2.17. Devices Should Log Every Message . . . . . . . . . . . . . 20
     2.18. Syslog-specific Capabilties  . . . . . . . . . . . . . . . 21
       2.18.1.  Configurable Facility Values  . . . . . . . . . . . . 21
       2.18.2.  Configurable Destination UDP Port . . . . . . . . . . 22
     2.19. SNMP-specific capabilities . . . . . . . . . . . . . . . . 22
       2.19.1.  Read-only Operations Supported  . . . . . . . . . . . 23
       2.19.2.  Restrict Returning Data to specific Hosts . . . . . . 23
       2.19.3.  Only Return Specific Data to Requestor  . . . . . . . 24
   3.  Additional Operational Practices . . . . . . . . . . . . . . . 25
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . . 26
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 27
   6.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 28
   7.  Normative References . . . . . . . . . . . . . . . . . . . . . 29
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 30
   Intellectual Property and Copyright Statements . . . . . . . . . . 31












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1.  Introduction

   This document defines a set of capabilities for network equipment
   that generates event logs or performs event logging in the
   environments defined by [RFC4778].  Its goal is to identify
   capabilities required of the network equipment to generate and
   forward messages from the network equipment to an event logging
   system.

   Although most people equate logging with using the syslog protocol,
   other protocols such as SNMP [RFC3411] are quite capable of
   generating a log entry for transmission to a remote log entry
   collector.

   RFC4778 defines the goals, motivation, scope, definitions, intended
   audience, threat model, and potential attacks for each of the
   practices currently in use by network operators.  Those current
   practices have been identified and refined to generate the
   capabilities listed in this document.

1.1.  Security Overview

   The logging capabilities defined in this document are derived from
   observations and experiences in real world networks where unexpected
   activities in a network infrastructure caused concern to the network
   operator.  Examples of such activities are:

      An adversary or unauthorized user login into an infrastructure
      device.  The risk is that the configuration or other operating
      parameter could be modified.

      A device becomes overwhelmed, throttles, or crashes.  Without
      logging or some other mechanism to notify the operator of the
      condition, the operator will not know that an action is required
      to return the device to optimal operating condition.

      Network problems cannot be properly diagnosed without sufficient
      information, which if not captured, will not be available for
      diagnoses activities.

   The main threat in a logging infrastructure is that a bad event may
   happen and the operator of the infrastructure may not be made aware
   of that event and cannot correct or respond to it.  This document is
   concerned solely with the ability of the network device to generate
   appropriate messages.  For guidance on transport and secure delivery
   see [RFC3164].  For a logging infrastructure introduction and
   guidance on building a secure infrastructure see NIST Publication
   800-62. [SP800-92]



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   One threat to the logging infrastructure is a self-inflicted denial
   of service attack due to an overwhelming amount of log messages
   generated on the local machine, such that the local system is using
   all its available effort to generate log messages, or congestion
   through the network between the log generator and the log collector,
   such that the remote system is inaccessible to management operations.
   Although not specifically a capability, care should be taken when
   configuring the logging infrastructure to account for this threat.

1.2.  Capabilities vs. Requirements

   Capabilities may or may not be requirements.  That is a local
   determination that must be made by each operator with reference to
   the policies that they must support.  This document, together with
   [RFC4778], will assist network operators in identifying their
   security capability requirements and communicating them clearly to
   vendors.

   Capabilities are defined without reference to specific technologies.
   This is done to leave room for deployment of new technologies that
   implement the capability.  Each capability cites the practices it
   supports.  Current implementations that support the capability are
   cited.

1.3.  Format

   Each capability has the following subsections:

   o  Capability (what)

   o  Discussion

   o  Supported Practices (why)

   o  Current Implementations (how)

   o  Considerations (caveats, resource issues, protocol issues, etc.)

   The Capability section describes a feature to be supported by the
   device.  The Supported Practice section cites practices described in
   [RFC4778] that are supported by this capability.  The Current
   Implementation section is intended to give examples of
   implementations of the capability, citing technology and standards
   current at the time of writing.  It is expected that the choice of
   features to implement the capabilities will change over time.  The
   Considerations section lists operational and resource constraints,
   limitations of current implementations, trade offs, etc.




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2.  Functional Capabilities of Log Generating Systems

   The capabilities in this section are intended to list testable,
   functional capabilities that are needed to operate devices securely
   and meet the obligations of Section 1.1Security Overview.

2.1.   Logging Facility Uses Protocols Subject To Open Review

   Capability

      The device is capable of providing a logging facility that is
      based on protocols subject to open review.  Custom or proprietary
      logging protocols MAY be implemented provided the same information
      is made available.

   Discussion

      The use of logging based on protocols subject to open review
      permits the operator to perform archiving and analysis of logs
      without relying on vendor-supplied software and servers.


   Supported Practices

      *  Use IETF-defined protocols such as syslog, syslog with reliable
         delivery, syslog-ng, or SNMP.


   Current Implementations

      This capability can be satisfied by the use of one or more of
      syslog [RFC3164], syslog with reliable delivery [RFC3195], TACACS+
      [RFC1492], RADIUS [RFC2865], or SNMP [RFC3415].

      The current best solution seems to be the following:

      *  Implement syslog [RFC3164].

      *  Consider implementing syslog with reliable delivery [RFC3195].

      *  Using SNMP with applicable security controls.


   Considerations







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      None.


2.2.  Logs Sent To Remote Servers

   Capability

      The device is capable of supporting transmission of records of
      security-related events to one or more remote collection devices.
      There should be configuration settings on the device that allow
      selection of destination servers.

   Discussion

      None.


   Supported Practices

      *  Use multiple collection devices to enhance reliability.

      *  Use different collection devices to segregate different event
         sensitivity levels.


   Current Implementations

      This capability may be satisfied by the use of one or more of:
      syslog [RFC3164], syslog with reliable delivery [RFC3195], TACACS+
      [RFC1492], or RADIUS [RFC2865].


   Considerations

      This capability is important because it supports individual
      accountability.  It is important to store them on a separate
      server to preserve them in case of failure or compromise of the
      managed device.

      Note that there may be privacy or legal considerations when
      logging/monitoring user activity.

      High volumes of logging may generate excessive network traffic
      and/or compete for scarce memory and CPU resources on the device.







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2.3.   Ability to Select Reliable Delivery

   Capability

      The device is able to select reliable delivery of log messages.

   Discussion

      Reliable delivery is important to the extent that log data is
      depended upon to make operational decisions and perform forensic
      analysis.  Without reliable delivery, log data becomes a
      collection of hints instead of a true record of events.


   Supported Practices

      *  Use syslog-ng.

      *  Tunnel the logging stream over a TCP-based connection.

      *  Use an out-of-band network to connect critical logging devices
         to the collection device.


   Current Implementations

      One example of reliable syslog delivery is defined [RFC3195].
      Syslog-ng provides another example, although the protocol has not
      been standardized


   Considerations

      Reliable delivery should be used if the path from log event
      generator to the collection device transits administrative domains
      or uses unreliable channels, as it is important that the entire
      stream of log events is captured.


      CAUTION: The use of reliable delivery is heavily debated within
      the logging and security communities as errors encountered when
      reliably logging can cause the log generator to repeatedly attempt
      to deliver the log message causing a denial of service or deadlock
      condition.  It may be desirable to use a rate-limiting features in
      syslog senders or for the logger of a message to have the option
      of either not log more messages or cease its own operation.  This
      document does not specify which options to use.




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2.4.   Ability to Remotely Log Securely

   Capability

      The device is capable of delivering log data stream to the
      collection device in a confidential manner.

   Discussion

      While syslog *could* provide this capability, it has many security
      issues and by itself does not address issues from the threat
      model.  See the security considerations section of [RFC3164] for a
      list of issues.  Syslog with reliable delivery provides solutions
      to most/all of these issues, however at the time of this writing
      there are few implementations.  Other possible solutions might be
      to tunnel syslog over a secure transport, but this often raises
      difficult key management and scalability issues.


   Supported Practices

      *  Log data tunnelled within IPSec or SSH.

      *  Use syslog-ng.

      *  Use security services supplied by SNMP [RFC3414]


   Current Implementations

      There is no common implementation of this capability.


   Considerations

      Delivering log data across untrusted streams or including
      sensitive data in a event data may require additional
      countermeasures to protect the data.  This concern should not be
      addressed lightly.

      ISPs are fully aware that there is no security with syslog but
      IPSec is considered too operationally expensive and cumbersome to
      deploy.  Syslog-ng and stunnel could be used for better
      authentication and integrity protected solutions.  Mechanisms to
      prevent unauthorized personnel from tampering with logs is
      constrained by auditing who has access to the logging servers and
      files.




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2.5.   Ability to Log Locally

   Capability

      The device is capable of logging data locally on the device itself
      into non-volatile storage.

   Discussion

      Logging of failed authentication attempts to local non-volatile
      storage is critical as it provides a record of events if the
      device gets isolated from its authentication interfaces or an
      attack overwhelms the console interface.  Local logging is also
      important for viewing information when connected to the device and
      it provides some backup of log data in case remote logging fails.

      Local logging also provides a way to quickly view logs relevant to
      one device without having to sort through a possibly large set of
      logs from other devices at the collection device.


   Supported Practices

      *  To conserve space, only failed device logins and network
         connectivity issues are logged locally.


   Current Implementations

      One example of local logging would be a memory buffer that
      receives copies of messages sent to the remote log server.

      Another example might be a local syslog server (assuming the
      device is capable of running syslog and has some local storage).





   Considerations

      Storage on the device may be limited.  High volumes of log
      messages may quickly fill the available storage, in which case
      there are two options: new logs overwrite old logs (possibly via
      the use of a circular memory buffer or log file rotation) or
      logging stops.





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2.6.   Ability to Log Different Severities to Different Destinations

   Capability

      The device is capable of specifying different severity levels of
      log message to be delivered to different collection destinations.

   Discussion

      A network of multiple devices may generate a significant amount of
      log data.  The ability to send critical log messages, for example
      a root login, to a specific destination device will enhance the
      ability of the network operator to notice the critical event.


   Supported Practices

      *  Email critical event notices to a continuously monitored
         mailbox.

      *  Send critical event notices to a separate log collector that
         scrolls received messages upon a large display in the NOC.


   Current Implementations

      There are no common implementations of this capability.


   Considerations

      The use of multiple collectors will incur maintenance and
      reliability issues.  In some cases, multiple filters watching a
      single collection point may be more efficient than using multiple
      collectors.


2.7.   Ability to Log to Multiple Destinations

   Capability

      The device is capable of allowing log message to be delivered to
      multiple collection destinations.

   Discussion






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      All ISPs have multiple syslog servers - some ISPs choose to use
      separate syslog servers for varying infrastructure devices (i.e.,
      one syslog server for backbone routers, one syslog server for
      customer edge routers, etc.).  This provides a backup mechanism to
      see what is going on in the network in the event that a device may
      'forget' to do syslog if the CPU is busy.


   Supported Practices

      *  Use multiple log servers to enhance reliability.


   Current Implementations

      Most ISPs use multiple, sometimes geographically diverse, log
      collectors.


   Considerations

      None.


2.8.   Ability to Maintain Accurate System Time

   Capability

      The device is capable of maintaining accurate, "high resolution"
      system time.

   Discussion

      Accurate time is important to the generation of reliable log data.
      Accurate time is also important to the correct operation of some
      authentication mechanisms.

      The ability to correlate network events from different devices is
      directly related to the accuracy of the log timestamps.  If a time
      line cannot be constructed, the event logs and forensic data are
      useless.


   Supported Practices

      *  The time is derived from NTP which is generally configured as a
         flat hierarchy at stratum-1 and stratum-2 servers to have less
         configuration and fewer maintenance issues.



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      *  Each router is configured with one stratum-1 peer both locally
         and remotely.


   Current Implementations

      This capability may be satisfied by supporting Network Time
      Protocol (NTP), Simple Network Time Protocol (SNTP), or via direct
      connection to an accurate time source.


   Considerations

      System clock chips are inaccurate to varying degrees.  System time
      should not be relied upon unless it is regularly checked and
      synchronized with a known, accurate external time source (such as
      an NTP stratum-1 server).  Also note that if network time
      synchronization is used, an attacker may be able to manipulate the
      clock unless cryptographic authentication is used.


2.9.   Display Timezone and UTC Offset

   Capability

      The device is capable of displaying and logging system time in a
      timezone or offset from UTC.

   Discussion

      None.


   Supported Practices

      *  The log timestamps include a timezone indicator like "-05:00".


   Current Implementations

      Many devices support this capability.










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   Considerations

      Knowing the timezone or UTC offset makes correlation of data and
      coordination with data in other timezones possible.  Bob is in
      Newfoundland, Canada which is UTC -3:30.  Alice is somewhere in
      Indiana, USA.  Some parts of Indiana switch to daylight savings
      time while others do not.  A user on Bob's network attacks a user
      on Alice's network.  Both are using logs with local timezones and
      no indication of UTC offset.  Correlating these logs will be
      difficult and error prone.  Including timezone, or better, UTC
      offset, eliminates these difficulties.

      Notice that a physical location may have different offsets from
      UTC during a year as summer time, daylight savings time, or other
      local customs are applied.


2.10.  Default Timezone Should Be UTC

   Capability

      The device is capable of using UTC for its default timezone for
      display and logging.  The device may be capable of supporting a
      mechanism to allow the operator to specify the display and logging
      of times in a timezone other than UTC.

   Discussion

      Knowing the timezone or UTC offset makes correlation and
      coordination in other timezones possible.

   Supported Practices

      *  The timezone offset can be entered as part of configuration of
         a device.


   Current Implementations

      Bob in Newfoundland (UTC -3:30) and Alice in Indiana (UTC -5 or
      UTC -6 depending on the time of year and exact county in Indiana)
      are working an incident together using their logs.  Both left the
      default settings, which was UTC, so there was no translation of
      time necessary to correlate the logs.







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   Considerations

      None.


2.11.   Log Entries Must Be Timestamped

   Capability

      By default, the device should be capable of generating timestamps
      on all log messages, accurate to within a second or less, and
      including a timezone.  The device should be capable of disabling
      the generation of timestamps.

   Discussion

      Accurate timestamps are necessary for correlating events,
      particularly across multiple devices or with other organizations.
      This applies when it is necessary to analyze logs.


   Supported Practices

      *  Each entry into the log contains a time value.


   Current Implementations

      This capability may be satisfied by writing timestamps into syslog
      messages.


   Considerations

      It is difficult to correlate logs from different time zones.
      Security events on the Internet often involve machines and logs
      from a variety of physical locations.  For that reason, UTC is
      preferred, all other things being equal.


2.12.   Log on Exception or Identified Event

   Capability

      The device is capable of generating log entries on exceptions
      (e.g., failures) or event matching (e.g., generate a log entry if
      an event happens) via a configurable value.




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   Discussion

      Traditionally, log events are generated on exceptions, such as
      failures or errors.  Often this is not sufficient as a network
      operator cannot tell if an attacker failed to log into a device
      once, or failed once and then succeeded on the second try.
      Devices should be configurable to allow for log messages on
      failures, successes, or everything.


   Supported Practices

      *  Log all login events to a device but have only the collection
         device alert on failures.

      *  Log successful device configuration changes since one must be
         aware of all modifications on some types of devices.


   Current Implementations

      Some ISPs put in passive devices to see routing updates and
      withdrawals, so that they do not rely solely on the device for log
      files.


   Considerations

      None.


2.13.   Logs Contain Untranslated IP Addresses

   Capability

      The device is capable of NOT using the DNS name of the log message
      generating device in event messages and logs.  The device will use
      the IP Address of the log message generator in its logs.

   Discussion

      Although sometimes less obtuse than DNS names, IP address
      assignments tend to be more stable than DNS entries.  If an
      operator is trying to correlate a historical event, the DNS name
      may have been changed from that used at the event.  To ease this
      confusion, the IP address of the source of the action that caused
      the log event should be retained in the log entry.




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   Supported Practices

      *  Include the source IP address in all log messages.

      *  Although a corresponding DNS name is useful, DNS lookups can be
         slow and consume resources.


   Current Implementations

      Most devices include the source IP in event logs


   Considerations

      A failed network login should generate a record with the source
      address of the login attempt, but the Source addresses may be
      spoofed.  Network-based attacks often use spoofed source addresses
      so they should not be completely trusted unless verified by other
      means.  Having accurate timestamps in the logs increases the
      chances that the use of an address can be correlated to an
      individual.


2.14.  Logs Contain Records Of Critical Security Events

   Capability

      The device is capable of generating a log event for at least the
      following events:



         * authentication successes

         * authentication failures

         * session Termination

         * authorization changes

         * configuration changes

         * device status changes







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   Discussion

      The main function of any of these log messages is to see what the
      device is doing, as well as to try and ascertain what certain
      malicious attackers are trying to do.

      Typically the data logged will contain the source and destination
      IP addresses and layer 4 port numbers as well as a timestamp.


   Supported Practices

      *  Examples of events recorded include: user logins, bad login
         attempts, logouts, user privilege level changes, configuration
         commands issued by privileged users, and system startup/
         shutdown events.


   Current Implementations

      Most devices crudely support this capability.


   Considerations

      This list is far from complete.  Note that there may be privacy or
      legal considerations when logging/monitoring user activity or
      personal information.

      This is an important capability because it supports individual
      accountability and auditing as well as forensics.  See section
      4.5.4.4 of The Site Security Handbook..


2.15.  Logs Contain Records of General Security Events

   Capability

      The device is capable of generating a log record for all other
      critical security related events including filtering (or ACL)
      exceptions, routing protocol state changes, all device access
      (regardless of authentication success or failure), all commands
      issued to a device, and all routing events (boot-up/flaps).

   Discussion






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      The main function of any of these log messages is to see what the
      device is doing as well as to try and ascertain what certain
      malicious attackers are trying to do.

      Typically the data logged will contain the source and destination
      IP addresses and layer 4 port numbers as well as a timestamp.


   Supported Practices

      *  Examples of events recorded include: ACL matches, filtering
         exceptions, and individual configuration commands issued by
         users.


   Current Implementations

      Most devices crudely support this capability.


   Considerations

      This list is far from complete.  Note that there may be privacy or
      legal considerations when logging/monitoring user activity or
      personal information.

      This is an important capability because it supports individual
      accountability and auditing as well as forensics.  See section
      4.5.4.4 of the Site Security Handbook [RFC2196].


2.16.  Logs Do Not Contain Passwords

   Capability

      The device is capable of excluding passwords, by default
      configuration, from all audit records, including records of
      successful or failed authentication attempts.

   Discussion

      A user may make small mistakes in entering a password such as
      using incorrect capitalization ("my password" vs. "My Password").
      Event logs are traditionally dispersed widely so unexpected events
      will be noticed.  Unauthorized access to event logs that contain
      these mistakes may compromise more than just the network devices
      as most users do not have independent passwords for every system.




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   Supported Practices

      *  Login failure log messages include the failed username,
         timestamp, and source IP address, but not the password used.


   Current Implementations

      Access control and authorization requirements differ for
      accounting records (logs) and authorization databases (passwords).
      Logging passwords may grant unauthorized access to individuals
      with access to the logs.  Logging failed passwords may also give
      hints about actual passwords.  See section 4.5.4.4 of Site
      Security Handbook [RFC2196].




   Considerations

      There may be situations where it is appropriate/required to log
      passwords, such as when performing real-time attack analysis.
      Caution is advised in these rare circumstances.

      Even with that caution, there's a remaining risk with logging user
      names, since many users accidentally type in their password for
      the username.  One way to mitigate this risk is to log only
      usernames that actually do exist but this adds considerate
      complexity to a logging system and might allow a different attack
      vector.


2.17.  Devices Should Log Every Message

   Capability

      Devices should be capable of being configured to either log every
      event or to drop events due to congestion.

   Discussion

      Many devices implement logging as an afterthought with the device
      dropping log messages or failing to log critical events when the
      device is "busy".  This behaviour makes forensic analysis
      difficult, if not impossible.  Devices should be configurable to
      not drop log events at those operator-defined times when this
      behaviour is expected.




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   Supported Practices

      *  Use multiple logging devices and collectors to capture enough
         extra messages to be able to recreate a full log.


   Current Implementations

      Use multiple logging devices.




   Considerations

      Improper configuration or implementation of this capability may
      open a device, network, or logging infrastructure to a self-
      inflicted denial of service attack..


2.18.  Syslog-specific Capabilties

   The predominant logging mechanism within network infrastructures is
   BSD-syslog and its variants.  With such widespread use, this section
   identifies capabilities specific to syslog.

2.18.1.  Configurable Facility Values

   Capability

      The device is capable of allowing for the selection of the syslog
      facility number via configuration.

   Discussion

      A network operator may have many similar devices in their network.
      The ability to segregate different severity events by the
      strategic use of the syslog facility number is extremely useful.


   Supported Practices

      *  Authentication log entries are marked at a different facility
         code to allow for easier segregation at the event collector.







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   Current Implementations

      Some devices support this capability via a configuration variable.


   Considerations

      None.


2.18.2.   Configurable Destination UDP Port

   Capability

      Devices are capable of allowing for the configuration of the
      destination syslog EDP port number.

   Discussion

      In large logging environments, spreading the load amongst multiple
      receiving daemons is a useful optimization.  This capability also
      allows operators to differentiate between different device
      functions very easily, for example all backbone router log to port
      512 and all access router log to port 513.


   Supported Practices

      *  Send all backbone routers log to port 512 and all access router
         log to port 513.


   Current Implementations

      Some devices support this capability via a configuration variable.


   Considerations

      None.


2.19.  SNMP-specific capabilities

   Another common logging mechanism uses the notification messages of
   the Simple Network Management Protocol [RFC3411].





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2.19.1.   Read-only Operations Supported

   Capability

      The device is capable of disabling SNMP write operations to the
      device.

   Discussion

      Since SNMP is used as a management protocol in addition to its
      logging functionality, the ability to disable operations that
      would change the device operations should be supported for those
      devices which aren't using the management functions.


   Supported Practices

      *  Disable SNMP write operations.


   Current Implementations

      Some devices support this capability via a configuration variable.


   Considerations

      None.


2.19.2.  Restrict Returning Data to specific Hosts

   Capability

      The device is capable of restricting the IP addresses that can
      query the SNMP interface for event data.

   Discussion

      Since event data can educate an adversary, devices should be able
      to only send event data ("responses") to certain, configured IP
      addresses, not any system that interrogates them.  See [RFC3413].


   Supported Practices

      *  Configure devices to only accept SNMP requests from authorized
         addresses.



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   Current Implementations

      Some devices support this capability via a configuration variable.


   Considerations

      None.


2.19.3.  Only Return Specific Data to Requestor

   Capability

      The device is capable of delivering specific managed object data
      (e.g., values linked to a specific OID) instead of returning all
      event data for the device (e.g., an entire OID subtree).

   Discussion

      Since event data can educate an adversary, devices should be able
      to only send specific event data instead of returning all the data
      in every query.  See [RFC3415].


   Supported Practices

      *  Queries request specific OID values instead of dumping the
         entire MIB.  This practice reduces event data volume in
         addition to attaining security.


   Current Implementations

      Most devices support this capability.


   Considerations

      None.











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3.  Additional Operational Practices

   This section describes practices not covered in [RFC4778].  They are
   included here to provide justification for capabilities that
   reference them.

   This section will be populated from comments received on this
   internet-draft.











































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4.  Security Considerations

   Security capabilities of network devices is the subject matter of
   this entire memo.  The capabilities listed cite practices in
   [RFC4778] that they are intended to support.  [RFC4778] also defines
   the general threat model, practices, and lists justifications for
   each practice.












































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5.  IANA Considerations

   There are no IANA actions required by this document.
















































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6.  Acknowledgments


















































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7.  Normative References

   [RFC1492]  Finseth, C., "An Access Control Protocol, Sometimes Called
              TACACS", RFC 1492, July 1993.

   [RFC2196]  Fraser, B., "Site Security Handbook", RFC 2196,
              September 1997.

   [RFC2865]  Rigney, C., Willens, S., Rubens, A., and W. Simpson,
              "Remote Authentication Dial In User Service (RADIUS)",
              RFC 2865, June 2000.

   [RFC3164]  Lonvick, C., "The BSD Syslog Protocol", RFC 3164,
              August 2001.

   [RFC3195]  New, D. and M. Rose, "Reliable Delivery for syslog",
              RFC 3195, November 2001.

   [RFC3411]  Harrington, D., Presuhn, R., and B. Wijnen, "An
              Architecture for Describing Simple Network Management
              Protocol (SNMP) Management Frameworks", STD 62, RFC 3411,
              December 2002.

   [RFC3413]  Levi, D., Meyer, P., and B. Stewart, "Simple Network
              Management Protocol (SNMP) Applications", STD 62,
              RFC 3413, December 2002.

   [RFC3414]  Blumenthal, U. and B. Wijnen, "User-based Security Model
              (USM) for version 3 of the Simple Network Management
              Protocol (SNMPv3)", STD 62, RFC 3414, December 2002.

   [RFC3415]  Wijnen, B., Presuhn, R., and K. McCloghrie, "View-based
              Access Control Model (VACM) for the Simple Network
              Management Protocol (SNMP)", STD 62, RFC 3415,
              December 2002.

   [RFC3871]  Jones, G., "Operational Security Requirements for Large
              Internet Service Provider (ISP) IP Network
              Infrastructure", RFC 3871, September 2004.

   [RFC4778]  Kaeo, M., "Operational Security Current Practices In
              Internet Service Provider Environments", January 2007.

   [SP800-92]
              Souppaya, M. and K. Kent, "Guide to Security Log
              Management", FIPS 800-92, April 2006.





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Authors' Addresses

   Patrick Cain
   The Cooper-Cain Group, Inc.
   P.O. Box 400992
   Cambridge, MA  02140
   U.S.A.

   Phone: +1 617-848-1950
   Email: pcain@coopercain.com


   George Jones

   Email: gmj3871@pobox.com




































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Full Copyright Statement

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