Internet Engineering Task Force                     Dominique Brezinski
INTERNET-DRAFT                                                    [...]
Valid for six months                                       Tom Killalea
                                                             March 2000

            Guidelines for Evidence Collection and Archiving


Status of this Memo

   This document is an Internet-Draft and is in full conformance with
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Copyright Notice

   Copyright (C) The Internet Society (2000).  All Rights Reserved.


   The purpose of this document is to provide System Administrators with
   guidelines on the collection and archiving of evidence.

Table of Contents

   1 Introduction
     1.1 Conventions Used in this Document

   2 Guiding Principles during Evidence Collection
     2.1 Order of Volatility

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     2.2 Things to avoid

   3 The Collection Procedure

   4 The Archiving Procedure
     4.1 Chain of Custody
     4.2 The Archive

   5 Tools you'll need

   6 Security Considerations

   7 Author's Address

   8 Full Copyright Statement

1 Introduction

   The purpose of this document is to provide System Administrators with
   guidelines on the collection and archiving of evidence.  It's not our
   intention to insist that all System Administrators rigidly follow
   these guidelines every time they have a security incident.  Rather,
   we want to provide guidance on what they should do if they elect to
   collect and protect information relating to an intrusion.

   Such collection represents a considerable effort on the part of the
   System Administrator.  In addition, great progress has been made in
   recent years to speed up the re-installation of the Operating System
   and the reversion of a system to a 'trusted state', thus making the
   provide easy ways of archiving evidence (the difficult option).
   Further, increasing disk and memory capacities and the more
   widespread use of stealth and cover-your-tracks tactics by attackers
   have exacerbated the problem.

   If evidence collection is done correctly, it is much more useful in
   apprehending the attacker, and stands a much greater chance of being
   admissible in the event of a prosecution.

   You should use these guidelines as a basis for formulating your
   site's evidence collection procedures, and should incorporate your
   site's procedures into your Incident Handling documentation.  The
   guidelines in this document may not be appropriate under all
   jurisdictions.  Once you've formulated your site's evidence
   collection procedures, you should have law enforcement for your
   jurisdiction confirm that they're adequate.

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1.1 Conventions Used in this Document

   The key words "REQUIRED", "MUST", "MUST NOT", "SHOULD", "SHOULD NOT",
   and "MAY" in this document are to be interpreted as described in "Key
   words for use in RFCs to Indicate Requirement Levels" [RFC2119].

2 Guiding Principles during Evidence Collection

     - Adhere to your site's Security Policy and engage the appropriate
       Incident Handling and Law Enforcement personnel.

     - Capture as accurate a picture of the system as possible.

     - Keep detailed notes.  These should include dates and times.
       If possible generate an automatic transcript.
       (e.g., The 'script' program can be used, however the output file
       it generates should not be to media that is part of the

     - Be prepared to testify (perhaps years later) outlining all
       actions you took and at what times.  Detailed notes will be

     - Minimise changes to the data as you are collecting it.  This is
       not limited to content changes; you should avoid updating file or
       directory access times.

     - Remove external avenues for change.

     - When confronted with a choice between collection and analysis you
       should do collection first and analysis later.

     - Though it hardly needs stating, your procedures should be
       implementable.  If possible procedures should be automated for
       reasons of speed and accuracy.  Be methodical.

     - Speed will often be critical so your team should break up and
       collect evidence from multiple systems (including network
       in parallel.  However on a single given system collection should
       be done step by step, strictly according to your collection

     - Proceed from the volatile to the less volatile (see the Order of
       Volatility below).

     - You should make a bit-level copy of the system's media.  If you

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       wish to do forensics analysis you should make a bit-level copy of
       your evidence copy for that purpose, as your analysis will almost
       certainly alter file access times.  Avoid doing forensics on the
       evidence copy.

2.1 Order of Volatility

   When collecting evidence you should proceed from the volatile to the
   less volatile.  Here is an example order of volatility for a typical

     - Registers, cache

     - routing table, arp cache, process table, kernel statistics

     - Memory

     - temporary file systems

     - Disk

2.2 Things to avoid

   It's all too easy to destroy evidence, however inadvertently.

     - Don't shutdown until you've completed evidence collection.  Much
       evidence may be lost and the attacker may have altered the
       startup scripts/services to destroy evidence.

     - Don't trust the programs on the system.  Run your evidence
       programs from your Forensics CD (see below) or similar read-only

     - Don't run programs that modify the access time of all files on
       the system (e.g., 'tar' or 'xcopy').

3 The Collection Procedure

   [more text needed here]

4 The Archiving Procedure

   Evidence must be strictly secured.  In addition, the Chain of Custody

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   needs to be clearly documented.

4.1 Chain of Custody

   The following need to be documented

     - Where, when and by whom discovered.

     - Where, when and by whom was the evidence handled or examined.

     - Who had custody of the evidence, during what period.  How was it

     - When the evidence changed custody, when and how did the transfer
       occur (include shipping numbers, etc.)

4.2 Where and how to Archive

   If possible commonly used media (rather than some obscure storage
   media) should be used for archiving.

   [more text needed here]

5 Tools you'll need

   You should have the programs you need to do evidence collection and
   forensics on read-only media (e.g., CD).  You should have prepared
   such a CD for each of the Operating Systems that you manage in
   advance of having to use it.  When your systems are in production you
   might consider leaving a Forensics CD in the CD drive of each system,
   especially if your systems rarely need to use the CD drive after the
   installation process.

   Your forensics CD should include

     - a program for examining processes (e.g., 'ps').

     - programs for examining system state (e.g., 'showrev', 'ifconfig',
       'netstat', 'arp').

     - a program for doing bit-to-bit copies (e.g., 'dd').

     - programs for generating core images and for examining them (e.g,
       'gcore', 'gdb').

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     - scripts to automate evidence collection (e.g., The Coroner's
       Toolkit [FAR1999]).

   You should be prepared to testify to the authenticity and reliability
   of the tools that you use.

6 References

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
     Requirement Levels", RFC 2119, March 1997.

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

   [RFC2350] Brownlee, N., and  E. Guttman, "Expectations for Computer
     Security Incident Response", RFC 2350, June 1998.

     Farmer, D., and W Venema, "Computer Forensics Analysis Class

7 Acknowledgements

   We gratefully acknowledge the constructive comments received from
   Barbara Y. Fraser and Floyd Short.

6 Security Considerations

   This entire document discusses security issues.

7 Authors' Addresses

   Dominique Brezinski
   P.O. Box 81226
   Seattle, WA 98108-1226

   Phone: +1 206 266-6900

   Tom Killalea
   P.O. Box 81226
   Seattle, WA 98108-1226

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   Phone: +1 206 266-2196

8 Full Copyright Statement

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

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   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an

This document expires September 10, 2000.

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