1. 2008 CSI Challenge

2. Welcome to the 2008 CSI Challenge: Computer Forensics
What you will find in this presentation
What is computer forensics?
The four “A”s
How disk storage works in your case
How files live on disk
Where evidence might reside
What is slack space?
What is unallocated space?
Hex & Ascii representation
Tools
Steganography, recovering hidden data
Requirements
Glossary

3. What is Computer Forensics?
Digital version of “CSI”
Finds evidence of incidents on digital equipment
Computers & drives
PDA’s
iPods
Cell phones
Digital camera & flash cards
Network equipment
Evidence must stand up in court

4. The 4 A’s
Acquire
Archive
Analyze
Attest

5. Acquisition Crime Scene Considerations
Identify and acquire the evidence
Safeguard and process physically
Prints and trace evidence
Handling of Magnetic media (drives and floppies, etc)
Keep away from magnets, machinery which generate magnetic fields and static electricity (no plastic evidence bags to generate static electricity)
Note where found, under what circumstances
Nature of material expands where it might be hidden
Between pages of a book
Inside a device
Locate material which may assist
User manuals, lists, password which might be written down

6. Acquisition Identify sources of information
hard drives
disks (floppy, CD, DVD)
other devices
Digital cameras
Cell phones
PDA’s
Technician must understand technology required to ‘archive’ information
Once seized as evidence, the technician will then create a bit-for-bit forensic image and make it available to the analyst

7. Acquisition: Bit image
Image is a ‘bit-for-bit’ snapshot of the disk
This image is used by the analyst
The image contains everything on the disk
Files, deleted files, “dead space” on disk, etc…
Can’t read it directly
The forensic software ‘interprets’ the image and “sees” all the files on the disk
NEVER use the original media unless no other alternative… always use the bit-for-bit image if possible
If you ever need to use the original material, document it along with the reason
2008 CSI Challenge
Teams will be provided a ‘bit-for-bit image’ for analysis
Your team will not have to create this image

8. Analysis Examination of your evidence In Forensic Toolkit (FTK)
Create a New or Open an Existing case
Add evidence to the case
Drive (hard disk, floppy, USB flash drive, etc)
Previously acquired bit-image
2008 CSI Challenge teams will use this option
A Folder and its contents
Individual files

9. Analysis Find the evidence Examine the structure of the disk itself
hidden data
Suspicious files
Renamed, altered or deleted
Search for ‘strings’
( a string is a group of characters, such as a name, credit card number, or even a fragment of a word)
in files
in deleted files
in ‘dead space’ (slack or unallocated, explained later)

10. Analysis Look for ‘stuff’ in plain sight Look for hidden evidence
Files, s, etc
Look for hidden evidence
Files renamed to appear as different file types
Word document renamed as a ‘jpg’ image file
Stego’d file (see later)
Encrypted files
Password required
Locate password
In existing evidence
At crime scene
Guess password (important dates, names, etc)
Might require personal knowledge about suspect’s background
‘Crack’ the password using a computer program
(not an option for 2008 CSI Challenge… not enough time)

11. Analysis File anomalies (irregularities)
File name does not match the file type
An internal “signature” in the file indicates the type of file
Signatures are also called “magic numbers”
“JFIF” inside a file might mean it’s really a JPG image file and not a text file or whatever the filename indicates
File times are inconsistent
MAC times (Modification-Access-Creation)
It’s possible for creation time to be post-modification time, depending on OS and how file copied, etc..
Compressed files (zip or other format)
May be passworded, contain many files bundled into one file
You should know how to “unzip” a file if it’s compressed or “zipped”
File ends in ‘.zip’

12. Analysis Critical thinking: the investigative part!
incriminating evidence
(or exculpatory… excluding a suspect)
discovering new avenues of inquiries s
Recently used documents
visited websites
Snippets or fragments of information
Including slack space…

13. Archive
Saving the evidence for future use once you’re done with the case
In case you need to review your work

14. Attest Reporting of analysis results Testimony
written competency
Testimony
expert witness
verbal and non-verbal skills
Any reporting of results by 2008 CSI Challenge teams should be clear, legible, using whole sentences to state your findings

15. Explaining units of storage
This is a basic explanation of how information is stored on a computer’s disk
Byte
The basic unit of storage
Roughly equivalent to a ‘character’
1,000,000 byte =1 Megabyte (1 Mb)
Holds about a million typewritten characters
Sector
How bytes are organized on disk
512 bytes per sector
Cluster
A group of sectors
Floppy disk: 1 sector per cluster
Hard drive: depends on system

16. How a file is written Sectors are grouped into ‘clusters’
a cluster can be
1 sector/cluster (512 bytes)
2 sectors/cluster (1024 bytes)
4 sectors/cluster (2048 bytes)
8 sectors/cluster (4096 bytes)
on a floppy, we use one sector / cluster
when we need space for a file, the system gives us a cluster (not just a sector)

17. Slack Space When we write a file using a cluster
We have “left over” room in the cluster
This is called “slack space”
Information can reside in slack space
Cannot say that the person who wrote the file in that cluster also put that slack information into that cluster
Clusters can be reused once a file is deleted
They’re put back into a pool of unallocated clusters
(they don’t belong to any file)
If these clusters haven’t been used for writing a new file, it’s possible to recover this ‘deleted’ file

18. Cluster and slack space
Cluster (512 bytes)
we write about 100 bytes
the rest is ‘slack’
File
This is an example of a cluster containing information….blah blah blah…
Dear Sir; We have read your proposal, and … no thanks
Slack

19. Oh no! Should I worry about Hexadecimal
No, for the 2008 CSI Challenge you might see hexadecimal notation of the disk’s data, along with the “English” readable data
This is presented so that you’ll recognize it when you see it while using FTK (see the next screen)
You will not be responsible for knowing “hex”
Computers really only know “numbers”
Certain numbers (values) are associated with letters of the alphabet
For example a value of “44” in hexadecimal is a capital “D”, and a hex “20” is a space, a “64” value is a small “d”
This is called the ASCII code

20. Hex Data (numeric) and ASCII (Alpha)
Upper Case “D”

21. Tools
Software such as FTK (which you will be using) contain tools that allow you to:
Acquire an evidence image
Identify deleted files
Possibly recover a deleted file
Search the bit image
Search for string of text (last name, etc)
Identify files containing the string
Identify that area as belonging to a file, or in slack space
Examine attributes of files
Hidden
Deleted
File times
Mismatch between file name and actual file type
‘bad signature’ (txt file might actually be a ‘jpg’ file)
Show thumbnails of picture type files
Export files (or fragments) (collect them in one spot)
Bookmark critical findings (highlight relevant findings)
Document case for report (times, investigator, etc)

22. Tools Existing software PKZIP, WinZip, WinRAR Steganograhpy (S-Tools)
Word, Adobe, etc
Open files of that format
Analyst must know how the application software works
PKZIP, WinZip, WinRAR
Extract compressed files
Steganograhpy (S-Tools)
Extract files from a “stego’d” file
S-Tools will use BMP, GIF or WAV files as ‘containers’ to hide other files
Can be used to reveal and extract hidden files

23. FTK Forensic ToolKit (AccessData)
Demo version allows examination of cases with a max of 5000 files
Add your evidence image file
Analyze it
Document your results
You will use FTK to add your evidence to a new case and analyze it

24. Steganography Hidden information inside a file
A file inside a file (container file and message file)
Can be passworded / encrypted
The “container” (stego’d) file is either a “bmp” or “gif” image type
Can also be an ‘audio’ file
On a hard drive, or on someone’s iPod, etc…
Files can be included in a Word (or other document), such as webpages or be a “standalone” file on someone’s hard drive
S-Tools can be downloaded to reveal stego’d evidence

25. 2008 CSI Challenge Requirements
Laptop
CD / ROM drive
Software
Windows XP or Vista
Microsoft Office (2003 or better)
Access Data’s Forensic ToolKit (FTK)
S-tools
WinZip or capability to unzip files on your drive
Should already be built into Windows when you right-click on a zipped filename
Tutorials (including this) can be found on the website

26. Glossary ASCII Bit Byte
Computers only know numbers. ASCII is a ‘code’ that associates numbers with letters or characters of the alphabet.
Bit
Binary digit; a ‘one’ or a ‘zero’
Byte
Grouping of eight bits, representing a numerical value from 0 to 255
Can also represent a “character” or letter of the alphabet

27. Glossary Bit-for-bit image Bitstream image
Also known as a bitstream image
A “snapshot” of a piece of evidence, taken in a forensically sound manner (no alteration of original evidence)
Bitstream image
See bit-for-bit image

28. Glossary Cluster Compression (of files)
A group of sectors. Files are written by the system using clusters
Floppy clusters are 1 sector per cluster
Hard drives vary (common to find 8 sectors / cluster)
Compression (of files)
a method of making a large file smaller, by eliminating repetitive sequences of characters
See “zip” files

29. Glossary Encryption Evidence Hexadecimal
Used to make information unreadable unless you have a password
Evidence
Something that provides proof
Could be a hard drive, floppy, USB device, paper notes or anything containing information
Hexadecimal
Numerical representation used by computer scientists. See ASCII code

30. Glossary Password Slack or slack space Steganography
A mechanism which prevents a person from accessing a file unless a user provides the correct password or passphrase.
Slack or slack space
That area of a cluster belonging to a file, which is “left over.” Information can be contained in slack space.
Steganography
“Hidden writing.” The process of hiding information inside a container file. The container picture typically looks no different after having hidden data inside it. Software such as S-Tools is used both to hide as well as reveal information.

31. Glossary
Zip file
A compressed file. A zip can contain a single file, or many files. The zip file can contain a directory (folder) structure, along with all the files in that folder. Zip files can also be passworded.

32. 2008 CSI Challenge Good luck to all contestants
End of PowerPoint presentation