Digital Forensics and Flux Capacitors.pdf - SANS Computer Forensics

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Digital Forensics and Flux Capacitors.pdf - SANS Computer Forensics

Three things that irritate me…


Don‟t look

directly into

his eyes.

He‟ll steal

your soul!


If anyone

says “Aw!”

the kitten

meets

Mr. Pitbull


• It was a Trojan/Virus

• I was hacked

• My cat did it

• It was Aliens

• It was God

Yes, these are all real-world examples


Something from a recent case of mine…

• Guy has company laptop

• Guy surfs porn

• Guy gets fired

• Guy sues company

• Company hires me


My Findings:

This guys likes his porn… A

LOT*

*(not an actual quote from my report)


Guy hires a computer expert. His report

states:


“...the BIOS clock could be manually set

back... Once the computer is rebooted, the

operating system will take its current time

from the BIOS clock and any files created or

changed thereafter will reflect the (predated)

time as seen by the operating

system...


“There is no simple way of telling whether a

computer‟s BIOS clock has been „turned

back‟, especially if it was subsequently reset

to the correct time.”


One simple rule...

FUD Mini Rant

• Don‟t be stupid, only report the facts


Aim of this Presentation...

• To provide some ideas of how clock

changes can be tracked in Windows XP,

Vista, 7.

• Spur you on to find more

• Reduce the spreading of FUD


Windows Event Logs

• Default of 512KB in XP, 20MB in Vista,

Win7

• Sequentially written

• Overwritten from start when full

• Event IDs

• Date/time stamp


Vista, Win7

Event ID 1 in System log

“The system time has changed to 2011-01-

01T00:00:00.000000000Z from 2011-04-

01T10:17:04.137232300Z.”

Event ID 4616 in Security log

“The system time was changed.”


XP

Event ID 520 in Security log

“The system time was changed.”

Note that this will only work if “Audit privilege

use” is turned on. The default state is off.


Setupapi.log

• Logs first instance of a device being

connected

• Sequential logging

• Overwritten when full


$UsnJrnl·$J

• Typically may only hold data for a few

hours/days

• Data is stored sequentially

• Stores every file transaction during the

recorded time


$UsnJrnl·$J

·


$UsnJrnl·$J

Filename Date and Time

setupapi.app.log 31/05/2011 13:35

DLLHOST.EXE-FDE983AF.pf 31/05/2011 13:35

WMIPRVSE.EXE-1628051C.pf 31/05/2011 13:35

CONTROL.EXE-817F8F1D.pf 31/05/2011 13:36

RUNDLL32.EXE-89545801.pf 01/01/2010 14:36

RUNDLL32.EXE-D612ED71.pf 09/01/2010 11:01

launchy.ini 09/01/2010 11:03

MOBSYNC.EXE-C5E2284F.pf 09/01/2010 11:15

index.dat 31/05/2011 13:53

TASKHOST.EXE-7238F31D.pf 31/05/2011 13:53

launchy.ini 31/05/2011 13:53


$UsnJrnl·$J

Filename Date and Time

setupapi.app.log 31/05/2011 13:35

DLLHOST.EXE-FDE983AF.pf 31/05/2011 13:35

WMIPRVSE.EXE-1628051C.pf 31/05/2011 13:35

CONTROL.EXE-817F8F1D.pf 31/05/2011 13:36

RUNDLL32.EXE-89545801.pf 01/01/2010 14:36

RUNDLL32.EXE-D612ED71.pf 09/01/2010 11:01

launchy.ini 09/01/2010 11:03

MOBSYNC.EXE-C5E2284F.pf 09/01/2010 11:15

index.dat 31/05/2011 13:53

TASKHOST.EXE-7238F31D.pf 31/05/2011 13:53

launchy.ini 31/05/2011 13:53


Link Files

• Harry Parsonage‟s research

• Each link file has a sequence number

• Discrepancy is evidence of clock change


Link Files


Restore Points

• XP Restore Points are named sequentially

• Named in order of creation, clock is

ignored


Restore Points

Restore Point Creation Date/Time Restore Point Name

RP131 17:24:18 03/10/2011 System Checkpoint

RP132 18:08:39 03/11/2011 System Checkpoint

RP133 17:17:57 03/14/2011 Installation of Google Chrome

RP134 16:46:22 02/11/2011 Installation of Mozilla Firefox

RP135 10:03:12 03/15/2011 System Checkpoint

RP136 10:34:09 03/15/2011 Installation of Microsoft Office


Web Pages

• Many web pages contain their own clues

• Forums, news sites, sports sites, most

show the same thing…


Web Pages

• If this cached page showed a creation

date of May 17 2011 something is

obviously wrong


• NOT Sequential

• Still offer good clues

Index.dat Files

• Check the internet settings

• How often does the internet history

recycle?

• Large clock changes are easier to detect


Email Messages

• MSG/EML file has a creation date of May 17 2011

• Message properties suggest otherwise:

MIME-Version: 1.0 Received: by 10.68.14.37 with SMTP id

m5mr1406525pbc.474.1307239107883; Sat, 04 Jun 2011 18:58:27 -

0700 (PDT) Sender: harry@hogwarts.ac.uk Received: by 10.68.66.136

with HTTP; Sat, 4 Jun 2011 18:58:27 -0700 (PDT) Date: Sat, 4 Jun

2011 20:58:27 -0500 X-Google-Sender-Auth:

WiTe_KdGL5stt8fvjLC6pdnkRtY Message-ID:


Subject: Cloak of Invisibility From: Harry Potter

To: Hermione Granger,

Ron Weasley


Thumbnails

• In XP there is one thumbnail repository for

each folder

• In Vista/7 there is one set of files for all

thumbnails on the computer

• Both store information sequentially

regardless of the system clock


Example:

Thumbcache.db

• Forbidden pictures found on a suspect

machine

• Creation date suggests a specific user is

responsible

• What does the Thumbcache tell us?


Thumbcache.db

Offset (bytes) Creation Date/time of Original Picture

106 05/12/11 17:42:31

27890 05/12/11 17:42:38

55674 05/12/11 17:42:43

83458 05/12/11 17:42:55

110474 05/12/11 17:43:07

145554 02/11/11 11:03:56

173722 02/11/11 11:04:04

924742 05/12/11 17:46:22

954062 05/12/11 17:46:27


Thumbs.db

Offset (bytes) File Name Last Written

1456 Bella.jpg 05/24/11 23:57:09

34870 Edward.jpg 05/24/11 23:58:23

68284 Jacob.jpg 05/24/11 23:58:02

101698 Renee.jpg 03/13/11 11:17:12

135112 Jasper.jpg 05/25/11 00:02:32

168526 Alice.jpg 02/25/11 00:05:01

201940 Carlisle.jpg 02/25/11 00:06:49


Thumbnails - warning

• This MAY be due to clock change

• There are other explanations – what are

they?


Finally - New Technology

File systems

• Did the FS exist at the time?

Software version

• Metadata is key

File versions

• docx is a dead giveaway


Case Conclusion

• Opposing expert conceded no evidence of

clock change

• My client won case and costs against

former employee

• Evidence unFUDed


forensic4cast.com

@lee_whitfield

lee@forensic4cast.com


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