Archive for the ‘Análisis Forense Digital’ Category

Adjuntando un Medio Lógico y Físico a X-Ways Forensics

Posted by S3cTr4ck On September - 2 - 2010

Veamos como podemos realizar dicho procedimiento en un determinado caso forense.

Para ello tenemos creado y abierto nuestro caso en el entorno de análisis forense X-Ways Forensics. Desde allí vamos al menú del caso y seleccionamos File – Add Medium

Esto nos despliega la vista de dispositivos y medios.

Para el ejemplo, seleccioné un dispositivo USB (Unidad H). Nos muestra la información de anexo al caso, sistema de archivos, capacidad, etc.

Si requerimos anexar una imagen ya creada en otro proceso de recolección de evidencia, solo basta con ir al menú file – Add Image

Desde allí buscamos la ruta donde está almacenada la imagen-evidencia (.dd, x01, whx, e01, .001)

Finalmente en nuestros datos del caso, veremos un listado similar al siguiente

Si quisieramos explorar el contenido de estas evidencias, podemos utilizar las diferentes vistas del entorno de análisis.

En determinados casos de análisis forense digital se hace necesario incluir como evidencias diferentes fotografías de la escena o sitio que sea objeto de nuestra intervención y que de alguna manera estén implicadas en nuestro caso o puedan servir como prueba de que realmente estamos en el sitio referenciado y/o con los dispositivos relacionados.

Para una mejor relación de pruebas y análisis de datos podemos usar X-Ways Forensics como sistema de almacenamiento y enlace a dichos archivos fotográficos. Veamos entonces como podemos adjuntarlos a nuestro caso.

Desde el menu de X-Ways y situados en los datos de nuestro caso, vamos a File / Add File

Seleccionamos la fotografía a adjuntar. Una vez seleccionada nos encontramos con una imagen similar a la siguiente, en la cual se detallan algunos datos de la imagen (nombre, tamaño, fecha de creación, acceso), y un campo para la inclusión de comentarios que nos puedan servir como referencia en el caso.

Cuando ingremos los comentarios (opcionales), podemos generar una firma criptográfica (MD5, SHA1, PSCHF) correspondiente a la fotografía.

Una vez finalizados estos pasos, podríamos visualizar en cualquier momento la imagen adjunta, sin el riesgo de alterarla y con el objetivo de anexarla a nuestro reporte final.

Proteger Contra Escritura los Dispositivos USB en Windows

Posted by S3cTr4ck On August - 3 - 2010

Por diferentes razones podemos necesitar proteger contra escritura los dispositivos USB que se conecten a nuestro equipo (Distribución de Malware, Robo de información, etc). Pero para nuestro intereses particulares (Análisis Forense Digital) requerimos mantener en la mayor medida de lo posible, la no alteración de la evidencia informática. Es por ello que veremos como de manera rápida y efectiva, podremos proteger contra escritura los dispositvos USB que contengan evidencia y que sean objeto de una investigación o de un análisis forense digital. Veamos

Desde el editor de registro de windows (Regedit)

Vamos a HKEY_LOCAL_MACHINE >> SYSTEM >> CurrentControlSet >> Control


Ahora clic derecho Nueva Clave

Y creamos una nueva clave con el nombre de StorageDevicePolicies

En el panel derecho vamos a crear un nuevo valor DWORD

Ahora, para proteger contra escritura los dispositivos que se conecten, basta con asignarle dicho valor a 1 (uno). Para desactivar la protección asignamos 0 (cero).

Si quisieramos automatizar dicho procedimiento, solo basta con exportar la clave que generamos.

Podemos crear ambos estados (Protección ON – OFF) para facilitar la tarea.

El contenido de cada .reg debe ser similar al de la imagen

Por lo tanto, si requerimos activar la protección contra escritura de un dispositivo USB, solo tenemos que hacer doble click en la llave con el valor 1. Y si trataramos de escribir de alguna manera en dicho dispositivo, nos encontramos con la siguiente advertencia.

Continúa desde: Reto de Análisis Forense Digital de la Comunidad DragonJAR – Escenario e implementación

Vuelvo y repito que la intención de esta serie de post no es ofrecer el solucionario según los requerimientos exigidos por los desarrolladores del Reto. El objetivo de estos post es simplemente generar un espacio de discusión sobre los aportes que se realicen en pro de realizar de la mejor manera el análisis forense digital de dicho esceneario propuesto.

Read the rest of this entry »

Creando un Caso Forense en X-Ways Forensics

Posted by S3cTr4ck On July - 2 - 2010

Este corto post muestra el procedimiento para la creación de un nuevo caso en el entorno de trabajo X-Ways Forensics, veamos.

Desde el menu interno (Case Data) File, Create New Case

En la ventana de registro del caso, ingresamos los datos correspondientes a:

  • Título del Caso
  • Número del Caso (ID)
  • Descripción
  • Analista Forense
  • Organización
  • Dirección

La fecha y hora de generación de este nuevo caso, es automáticamente generada por la herramienta

Una vez completados los anteriores pasos, veremos en la pantalla de casos, nuestro nuevo registro

Es importante seleccionar siempre en el Menu View, Case Data, pues se requiere visualizar constantemente todos los datos relacionados con nuestro nuevo caso.

En próximos post veremos como podemos adjuntar archivos, imágenes y demás evidencia a nuestro caso.

Creando una Imagen Forense con X-Ways Forensics

Posted by S3cTr4ck On July - 1 - 2010

En el anterior post, presentaba de manera muy general entorno de trabajo forense X-Ways Forensics. Ahora vamos a comenzar una serie de post dedicados al trabajo práctico con dicha herramienta.

En este post veremos algunos métodos para la creación de imágenes forenses con dicha herramienta. Veamos.

Lo primero será ejecutar la herramienta desde el acceso directo creado en el proceso de instalación.

Desde el Menu Tools, Open Disk.

Seleccionaremos el disco fuente a tomar como evidencia.

Deberiamos ver una imagen similar a la siguiente

Una vez seleccionado el disco (físico/lógico), pasamos al menu File, Create Disk Image

Ahora seleccionamos las opciones de creación de imágenes. Para nuestro caso optamos por una imagen del tipo Raw image (.dd) y cálculo de hash por medio de MD5 a 128 bits

Veremos una barra de progreso como la siguiente

Proceso finalizado

Hash de la evidencia

Verificamos la evidencia en la ruta que seleccionamos previamente

Desde el mismo X-Ways Forensics podríamos explorar el contenido de la evidencia sin alterarla

Archivos

Para comprobar esta información, podríamos “montar” la evidencia adquirida con el software Mount Image Pro.

Pronto seguiremos con otros temas relacionados al uso de esta completa herramienta.

X-Ways Forensics, es un avanzado entorno de trabajo para analistas forenses que funciona sobre plataformas Windows 2000 / XP / 2003 / Vista / Seven / 2008 con tecnologías de 32 y 64 Bits.

Algunas de las características de X-Ways Forensics son:

  • Posibilidad de crear imágenes o copiados seguros de evidencias digitales.
  • Recuperación de información eliminada.
  • Visualizar estructuras de directorios sobre imágenes del tipo .dd.
  • Acceder a discos, RAIDs, e imágenes de gran tamaño (2Tb).
  • Soporte nativo para FAT12, FAT16, FAT32, TFAT, NTFS, Ext2, Ext3, Ext4, CDFS/ISO9660/Jolite, UDF.
  • Visualización y volcado de memoria RAM y memoria virtual de procesos en ejecución.
  • Creación de medios forenses estériles.
  • Generación y cálculo de firmas criptográficas (CRC32, MD4, ed2k, MD5, SHA-1, SHA-256, RipeMD.
  • Capacidades de búsquedas en la evidencia recolectada.
  • Bookmarks.
  • Anotaciones y un largo etc.

Para más información sobre X-Ways Forensics visita su Web oficial >>

Manual oficial de usuario para X-Ways forensics (pdf) >>

QuickStart Guide (pdf) >>

Los RFC (Request For Comments)(Petición de Comentarios) son una serie de documentos cuyo contenido es una propuesta oficial para un nuevo protocolo de la red o línea guía de desarrollo de un proceso, que explica con todo detalle para que en caso de ser aceptado pueda ser implementado sin ambiguedades.

Más información sobre los RFC >>

De esta manera la Guía RFC 3227 presenta un línea a seguir para los procesos de recolección y archivo de evidencias digitales en casos de análisis forense digital. Ofrece entonces una serie de mejores prácticas que permiten determinar el nivel de volatilidad de los datos, información a recolectar, almacenamiento y cadena de custodia. Para que estos puedan ser incluidos en procedimiento legales.

Veamos:

Network Working Group D. Brezinski
Request for Comments: 3227 In-Q-Tel
BCP: 55 T. Killalea
Category: Best Current Practice  neart.org
February 2002

Guidelines for Evidence Collection and Archiving

Status of this Memo

This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for   improvements.  Distribution of this memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

A “security incident” as defined in the “Internet Security Glossary”, RFC 2828, is a security-relevant system event in which the  system’s security policy is disobeyed or otherwise breached.  The purpose of   this document is to provide System Administrators with guidelines on   the collection and archiving of evidence relevant to such a security   incident.

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.

Table of Contents

1 Introduction
1.1 Conventions Used in this Document
2 Guiding Principles during Evidence Collection
2.1 Order of Volatility
2.2 Things to avoid
2.3 Privacy Considerations
2.4 Legal Considerations
3 The Collection Procedure
3.1 Transparency
3.2 Collection Steps
4 The Archiving Procedure
4.1 Chain of Custody
4.2 The Archive
5 Tools you’ll need
6 References
7 Acknowledgements
8 Security Considerations
9 Authors’ Addresses
10 Full Copyright Statement

1 Introduction

A “security incident” as defined in [RFC2828] is a security-relevant  system event in which the system’s security policy is disobeyed or otherwise breached.  The purpose of this document is to provide System Administrators with guidelines on the collection and archiving of evidence relevant to such a security incident.  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.  Great progress has been made in recent  years  to speed up the re-installation of the Operating System and to facilitate the reversion of a system to a ‘known’ state, thus making the ‘easy option’ even more attractive.  Meanwhile little has been done to 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.

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., On Unix systems the ‘script’ program can be used, however the output file it generates should not be to media that is part of the evidence).  Notes and print-outs should be signed and dated.
  • Note the difference between the system clock and UTC.  For each timestamp provided, indicate whether UTC or local time is used.
  • Be prepared to testify (perhaps years later) outlining all actions you took and at what times.  Detailed notes will be vital.
  • 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.  As with any aspect of an incident response policy, procedures should be tested to ensure feasibility, particularly in a crisis.  If possible procedures should be automated for reasons of speed and accuracy.  Be methodical.
  • For each device, a methodical approach should be adopted which follows the guidelines laid down in your collection procedure.

Speed will often be critical so where there are a number of devices requiring examination it may be appropriate to spread the work among your team to collect the evidence in parallel. However on a single given system collection should be done step by step.

  • 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 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 system.

  • Registers, cache
  • Routing table, arp cache, process table, kernel statistics, memory
  • Temporary file systems
  • Disk
  • Remote logging and monitoring data that is relevant to the system in question
  • Physical configuration, network topology
  • Archival media

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/shutdown scripts/services to destroy evidence.
  • Don’t trust the programs on the system.  Run your evidence gathering programs from appropriately protected media (see below).
  • Don’t run programs that modify the access time of all files on the system (e.g., ‘tar’ or ‘xcopy’).
  • When removing external avenues for change note that simply disconnecting or filtering from the network may trigger “deadman switches” that detect when they’re off the net and wipe evidence.

2.3 Privacy Considerations

  • Respect the privacy rules and guidelines of your company and your legal jurisdiction.  In particular, make sure no information collected along with the evidence you are searching for is available to anyone who would not normally have access to this information.  This includes access to log files (which may reveal patterns of user behaviour) as well as personal data files.
  • Do not intrude on people’s privacy without strong justification.  In particular, do not collect information from areas you do not normally have reason to access (such as personal file stores) unless you have sufficient indication that there is a real incident.
  • Make sure you have the backing of your company’s established procedures in taking the steps you do to collect evidence of an incident.

2.4 Legal Considerations

Computer evidence needs to be

  • Admissible: It must conform to certain legal rules before it can be put before a court.
  • Authentic: It must be possible to positively tie evidentiary material to the incident.
  • Complete: It must tell the whole story and not just a particular perspective.
  • Reliable: There must be nothing about how the evidence was collected and subsequently handled that casts doubt about its authenticity and veracity.
  • Believable: It must be readily believable and understandable by a court.

3 The Collection Procedure

Your collection procedures should be as detailed as possible.  As is the case with your overall Incident Handling procedures, they  should be unambiguous, and should minimise the amount of decision-making needed during the collection process.

3.1 Transparency

The methods used to collect evidence should be transparent and reproducible.  You should be prepared to reproduce precisely the methods you used, and have those methods tested by independent experts.

3.2 Collection Steps

  • Where is the evidence?  List what systems were involved in the incident and from which evidence will be collected.
  • Establish what is likely to be relevant and admissible.  When in doubt err on the side of collecting too much rather than not enough.
  • For each system, obtain the relevant order of volatility.
  • Remove external avenues for change.
  • Following the order of volatility, collect the evidence with tools as discussed in Section 5.
  • Record the extent of the system’s clock drift.
  • Question what else may be evidence as you work through the collection steps.
  • Document each step.
  • Don’t forget the people involved.  Make notes of who was there and what were they doing, what they observed and how they reacted.

Where feasible you should consider generating checksums and cryptographically signing the collected evidence, as this may make it easier to preserve a strong chain of evidence.  In doing so you must not alter the evidence.

4 The Archiving Procedure

Evidence must be strictly secured.  In addition, the Chain of Custody needs to be clearly documented.

4.1 Chain of Custody

You should be able to clearly describe how the evidence was found, how it was handled and everything that happened to it.

The following need to be documented

  • Where, when, and by whom was the evidence discovered and collected.
  • Where, when and by whom was the evidence handled or examined.
  • Who had custody of the evidence, during what period.  How was it stored.
  • 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.

Access to evidence should be extremely restricted, and should be clearly documented.  It should be possible to detect unauthorised access.

5 Tools you’ll need

You should have the programs you need to do evidence collection and forensics on read-only media (e.g., a CD).  You should have  prepared such a set of tools for each of the Operating Systems that you manage in advance of having to use it.

Your set of tools should include the following:

  • 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’, ‘SafeBack’).
  • Programs for generating checksums and signatures (e.g., ‘sha1sum’, a checksum-enabled ‘dd’, ‘SafeBack’, ‘pgp’).
  • Programs for generating core images and for examining them (e.g., ‘gcore’, ‘gdb’).
  • Scripts to automate evidence collection (e.g., The Coroner’s Toolkit [FAR1999]).

The programs in your set of tools should be statically linked, and should not require the use of any libraries other than those on the read-only media.  Even then, since modern rootkits may be installed through loadable kernel modules, you should consider that  your tools might not be giving you a full picture of the system.

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

6 References

[FAR1999]   Farmer, D., and W Venema, “Computer Forensics Analysis Class Handouts”, http://www.fish.com/forensics/

[RFC2119]   Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels”, BCP 14, RFC 2119, March 1997.

[RFC2196]   Fraser, B., “Site Security Handbook”, FYI 8, RFC 2196, September 1997.

[RFC2350]   Brownlee, N. and  E. Guttman, “Expectations for Computer Security Incident Response”, FYI 8, RFC 2350, June 1998.

[RFC2828]   Shirey, R., “Internet Security Glossary”, FYI 36, RFC 2828, May 2000.

7 Acknowledgements

We gratefully acknowledge the constructive comments received from Harald Alvestrand, Byron Collie, Barbara Y. Fraser, Gordon Lennox, Andrew Rees, Steve Romig and Floyd Short.

8 Security Considerations

This entire document discuses security issues.

9 Authors’ Addresses

Dominique Brezinski In-Q-Tel
1000 Wilson Blvd., Ste. 2900
Arlington, VA 22209 USA

EMail: dbrezinski@In-Q-Tel.org

Tom Killalea Lisi/n na Bro/n
Be/al A/tha na Muice Co. Mhaigh Eo
IRELAND

Phone: +1 206 266-2196
EMail: tomk@neart.org

10.  Full Copyright Statement

Copyright (C) The Internet Society (2002).  All Rights Reserved.

This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise  explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction  of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works.  However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case  the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English.

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 “AS IS” basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO  ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED  WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

Funding for the RFC Editor function is currently provided by the
Internet Society.

Network Working Group                                       D. Brezinski
Request for Comments: 3227                                      In-Q-Tel
BCP: 55                                                      T. Killalea
Category: Best Current Practice                                neart.org
                                                           February 2002

            Guidelines for Evidence Collection and Archiving

Status of this Memo

   This document specifies an Internet Best Current Practices for the
   Internet Community, and requests discussion and suggestions for
   improvements.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

   A "security incident" as defined in the "Internet Security Glossary",
   RFC 2828, is a security-relevant system event in which the system's
   security policy is disobeyed or otherwise breached.  The purpose of
   this document is to provide System Administrators with guidelines on
   the collection and archiving of evidence relevant to such a security
   incident.

   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.

Table of Contents

   1 Introduction.................................................... 2
     1.1 Conventions Used in this Document........................... 2
   2 Guiding Principles during Evidence Collection................... 3
     2.1 Order of Volatility......................................... 4
     2.2 Things to avoid............................................. 4
     2.3 Privacy Considerations...................................... 5
     2.4 Legal Considerations........................................ 5
   3 The Collection Procedure........................................ 6
     3.1 Transparency................................................ 6
     3.2 Collection Steps............................................ 6
   4 The Archiving Procedure......................................... 7
     4.1 Chain of Custody............................................ 7
     4.2 The Archive................................................. 7
   5 Tools you'll need............................................... 7

Brezinski & Killalea     Best Current Practice                  [Page 1]

RFC 3227           Evidence Collection and Archiving       February 2002

   6 References...................................................... 8
   7 Acknowledgements................................................ 8
   8 Security Considerations......................................... 8
   9 Authors' Addresses.............................................. 9
   10 Full Copyright Statement.......................................10

1 Introduction

   A "security incident" as defined in [RFC2828] is a security-relevant
   system event in which the system's security policy is disobeyed or
   otherwise breached.  The purpose of this document is to provide
   System Administrators with guidelines on the collection and archiving
   of evidence relevant to such a security incident.  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.  Great progress has been made in recent years
   to speed up the re-installation of the Operating System and to
   facilitate the reversion of a system to a 'known' state, thus making
   the 'easy option' even more attractive.  Meanwhile little has been
   done to 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.

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].

Brezinski & Killalea     Best Current Practice                  [Page 2]

RFC 3227           Evidence Collection and Archiving       February 2002

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., On Unix
         systems the 'script' program can be used, however the output
         file it generates should not be to media that is part of the
         evidence).  Notes and print-outs should be signed and dated.

      -  Note the difference between the system clock and UTC.  For each
         timestamp provided, indicate whether UTC or local time is used.

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

      -  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.  As with any aspect of an incident response
         policy, procedures should be tested to ensure feasibility,
         particularly in a crisis.  If possible procedures should be
         automated for reasons of speed and accuracy.  Be methodical.

      -  For each device, a methodical approach should be adopted which
         follows the guidelines laid down in your collection procedure.
         Speed will often be critical so where there are a number of
         devices requiring examination it may be appropriate to spread
         the work among your team to collect the evidence in parallel.
         However on a single given system collection should be done step
         by step.

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

Brezinski & Killalea     Best Current Practice                  [Page 3]

RFC 3227           Evidence Collection and Archiving       February 2002

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

      -  registers, cache

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

      -  temporary file systems

      -  disk

      -  remote logging and monitoring data that is relevant to the
         system in question

      -  physical configuration, network topology

      -  archival media

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/shutdown scripts/services to destroy evidence.

      -  Don't trust the programs on the system.  Run your evidence
         gathering programs from appropriately protected media (see
         below).

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

Brezinski & Killalea     Best Current Practice                  [Page 4]

RFC 3227           Evidence Collection and Archiving       February 2002

      -  When removing external avenues for change note that simply
         disconnecting or filtering from the network may trigger
         "deadman switches" that detect when they're off the net and
         wipe evidence.

2.3 Privacy Considerations

      -  Respect the privacy rules and guidelines of your company and
         your legal jurisdiction.  In particular, make sure no
         information collected along with the evidence you are searching
         for is available to anyone who would not normally have access
         to this information.  This includes access to log files (which
         may reveal patterns of user behaviour) as well as personal data
         files.

      -  Do not intrude on people's privacy without strong
         justification.  In particular, do not collect information from
         areas you do not normally have reason to access (such as
         personal file stores) unless you have sufficient indication
         that there is a real incident.

      -  Make sure you have the backing of your company's established
         procedures in taking the steps you do to collect evidence of an
         incident.

2.4 Legal Considerations

   Computer evidence needs to be

      -  Admissible:  It must conform to certain legal rules before it
         can be put before a court.

      -  Authentic:  It must be possible to positively tie evidentiary
         material to the incident.

      -  Complete:  It must tell the whole story and not just a
         particular perspective.

      -  Reliable:  There must be nothing about how the evidence was
         collected and subsequently handled that casts doubt about its
         authenticity and veracity.

      -  Believable:  It must be readily believable and understandable
         by a court.

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RFC 3227           Evidence Collection and Archiving       February 2002

3 The Collection Procedure

   Your collection procedures should be as detailed as possible.  As is
   the case with your overall Incident Handling procedures, they should
   be unambiguous, and should minimise the amount of decision-making
   needed during the collection process.

3.1 Transparency

   The methods used to collect evidence should be transparent and
   reproducible.  You should be prepared to reproduce precisely the
   methods you used, and have those methods tested by independent
   experts.

3.2 Collection Steps

      -  Where is the evidence?  List what systems were involved in the
         incident and from which evidence will be collected.

      -  Establish what is likely to be relevant and admissible.  When
         in doubt err on the side of collecting too much rather than not
         enough.

      -  For each system, obtain the relevant order of volatility.

      -  Remove external avenues for change.

      -  Following the order of volatility, collect the evidence with
         tools as discussed in Section 5.

      -  Record the extent of the system's clock drift.

      -  Question what else may be evidence as you work through the
         collection steps.

      -  Document each step.

      -  Don't forget the people involved.  Make notes of who was there
         and what were they doing, what they observed and how they
         reacted.

   Where feasible you should consider generating checksums and
   cryptographically signing the collected evidence, as this may make it
   easier to preserve a strong chain of evidence.  In doing so you must
   not alter the evidence.

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RFC 3227           Evidence Collection and Archiving       February 2002

4 The Archiving Procedure

   Evidence must be strictly secured.  In addition, the Chain of Custody
   needs to be clearly documented.

4.1 Chain of Custody

   You should be able to clearly describe how the evidence was found,
   how it was handled and everything that happened to it.

   The following need to be documented

      -  Where, when, and by whom was the evidence discovered and
         collected.

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

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

      -  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.

   Access to evidence should be extremely restricted, and should be
   clearly documented.  It should be possible to detect unauthorised
   access.

5 Tools you'll need

   You should have the programs you need to do evidence collection and
   forensics on read-only media (e.g., a CD).  You should have prepared
   such a set of tools for each of the Operating Systems that you manage
   in advance of having to use it.

   Your set of tools should include the following:

      -  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', 'SafeBack').

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RFC 3227           Evidence Collection and Archiving       February 2002

      -  programs for generating checksums and signatures (e.g.,
         'sha1sum', a checksum-enabled 'dd', 'SafeBack', 'pgp').

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

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

   The programs in your set of tools should be statically linked, and
   should not require the use of any libraries other than those on the
   read-only media.  Even then, since modern rootkits may be installed
   through loadable kernel modules, you should consider that your tools
   might not be giving you a full picture of the system.

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

6 References

   [FAR1999]   Farmer, D., and W Venema, "Computer Forensics Analysis
               Class Handouts", http://www.fish.com/forensics/

   [RFC2119]   Bradner, S., "Key words for use in RFCs to Indicate
               Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2196]   Fraser, B., "Site Security Handbook", FYI 8, RFC 2196,
               September 1997.

   [RFC2350]   Brownlee, N. and  E. Guttman, "Expectations for Computer
               Security Incident Response", FYI 8, RFC 2350, June 1998.

   [RFC2828]   Shirey, R., "Internet Security Glossary", FYI 36, RFC
               2828, May 2000.

7 Acknowledgements

   We gratefully acknowledge the constructive comments received from
   Harald Alvestrand, Byron Collie, Barbara Y. Fraser, Gordon Lennox,
   Andrew Rees, Steve Romig and Floyd Short.

8 Security Considerations

   This entire document discuses security issues.

Brezinski & Killalea     Best Current Practice                  [Page 8]

RFC 3227           Evidence Collection and Archiving       February 2002

9 Authors' Addresses

   Dominique Brezinski
   In-Q-Tel
   1000 Wilson Blvd., Ste. 2900
   Arlington, VA 22209
   USA

   EMail: dbrezinski@In-Q-Tel.org

   Tom Killalea
   Lisi/n na Bro/n
   Be/al A/tha na Muice
   Co. Mhaigh Eo
   IRELAND

   Phone: +1 206 266-2196
   EMail: tomk@neart.org

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RFC 3227           Evidence Collection and Archiving       February 2002

10.  Full Copyright Statement

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   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
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.

Brezinski & Killalea     Best Current Practice                 [Page 10]

La herramienta Maltego (desarrollada por Paterva) es una herramienta que permite realizar recolecciones de información en Internet así como la representación de la misma en formatos fáciles de interpretar.

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Estos son los solucionarios publicados por parte de HackPlayers (desarrolladores del primer reto de esteganografía publicado en Sec-Track y de quienes esperamos publiquen muchos más (Y)) y de Juanma Merino (quien desde un comienzo intentó resolverlo hasta conseguirlo, Felicitaciones Juanma ;) ).

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