The document discusses key aspects of computer forensics including its objectives, priorities, and tradeoffs between accuracy and speed. It describes the job of a forensics specialist which includes determining systems to collect evidence from, protecting and analyzing data, and producing reports. Applications in law enforcement, human resources, and other areas are covered. The document also outlines services provided, benefits of using professionals, issues that could occur, and comparing traditional versus computer forensics.

1. Objective and Priority
 Objective of Computer Forensics
- To recovery, analyze and present computer based
material in such a way that is it usable as evidence in a
court of law
- Note that the definition is the following: “computer
forensics, involves the preservation, identification,
extraction, and documentation of computer evidence
stored as data or magnetically encoded information”, by
John Vacca
 Priority
- Main priority is with forensics procedures, rules of
evidence and legal processes; computers are secondary
- Therefore accuracy is crucial

2. Accuracy vs Speed
 Tradeoffs between accuracy and speed
- E.g., Taking 4 courses in a semester vs. 2 courses; more
likely to get Bs and not As
- Writing a report in a hurry means likely less accurate
 Accuracy: Integrity and Security of the evidence is crucial
- No shortcuts, need to maintain high standards
 Speed may have to be sacrificed for accuracy.
- But try to do it as fast as you can provided you do not
compromise accuracy

3. The Job of a Forensics Specialist
 Determine the systems from which evidence is collected
 Protect the systems from which evidence is collected
 Discover the files and recover the data
 Get the data ready for analysis
 Carry out an analysis of the data
 Produce a report
 Provide expert consultation and/or testimony?

4. Applications: Law Enforcement
 Important for the evidence to be handled by a forensic expert;
else it may get tainted
 Need to choose an expert carefully
- What is his/her previous experience? Has he/she worked
on prior cases? Has he/she testified in court? What is
his/her training? Is he CISSP certified?
 Forensic expert will be scrutinized/cross examined by the
defense lawyers
 Defense lawyers may have their own possibly highly paid
experts?

5. Applications: Human Resources
 To help the employer
- What web sites visited?
- What files downloaded
- Have attempts been made to conceal the evidence or
fabricate the evidence
- Emails sent/received
 To help the employee
- Emails sent by employer – harassment
- Notes on discrimination
- Deleted files by employer

6. Applications: Other
 Supporting criminals
- Gangs using computer forensics to find out about
members and subsequently determine their whereabouts
 Support rogue governments and terrorists
- Terrorists using computer forensics to find out about
what we (the good guys) are doing
 We and the law enforcement have to be one step ahead of the
bad guys
 Understand the mind of the criminal

7. Services
 Data Services
- Seizure, Duplication and preservation, recovery
 Document and Media
- Document searched, Media conversion
 Expert witness
 Service options
 Other services

8. Data Services
 Data Seizure
- The expert should assist the law enforcement official in
collecting the data.
- Need to identify the disks that contain the data
 Data Duplication and Preservation
- Data absolutely cannot be contaminated
- Copy of the data has to be made and need to work with
the copy and keep the original in a safe place
 Data Recovery
- Once the device is seized (either local or remote) need to
use appropriate tools to recover the data

9. Data Services: Finding Hidden Data
 When files are deleted, usually they can be recovered
 The files are marked as deleted, but they are still residing in
the disk until they are overwritten
 Files may also be hidden in different parts of the disk
 The challenge is to piece the different part of the file together
to recover the original file
 There is research on using statistical methods for file
recovery
 http://www.cramsession.com/articles/files/finding-hidden-
data---how-9172003-1401.asp
 http://www.devtarget.org/downloads/ca616-seufert-
wolfgarten-assignment2.pdf

10. Document and Media Services
 Document Searches
- Efficient search of numerous documents
- Check for keywords and correlations
 Media Conversion
- Legacy devices may contain unreadable data. This data
ahs to be converted using appropriate conversion tools
- Should be placed in appropriate storage for analysis

11. Expert Witness Services
 Expert should explain computer terms and complicated processes in
an easy to understand manner to law enforcement, lawyers, judges
and jury
- Computer technologists and lawyers speak different languages
 Expertise
- Computer knowledge and expertise in computer systems,
storage
- Knowledge on interacting with lawyers, criminology
- Domain knowledge such as embezzlement, child exploitation
 Should the expert witness and the forencis specialist be one and the
same?

12. Service Options
 Should provide various types of services
- Standard, Emergency, Priority, Weekend After hours
services
 Onsite/Offsite services
 Cost and risks – major consideration
 Example: Computer Forensics Services Corporation
- http://www.computer-forensic.com/
- As stated in the above web site, this company provides
“expert, court approved, High Tech Investigations,
litigation support and IT Consulting.” They also
"Preserve, identify, extract, document and interpret
computer data. It is often more of an art than a science,
but as in any discipline, computer forensic specialists
follow clear, well-defined methodologies and procedures.”

13. Other Services
 Computer forensics data analysis for criminal and civil
investigations/litigations
 Analysis of company computers to determine employee
activity
- If he/she conducting his own business and/or
downloading pornography
- Surveillance for suspicious event detection
 Produce timely reports

14. Benefits of using Professional services
 Protecting the evidence
- Should prevent from damage and corruption
 Secure the evidence
- Store in a secure place, also use encryption technologies
such as public/private keys
 Ensure that the evidence is not harmed by virus
 Document clearly who handled the data and when - auditing
 Cleint/Attoney privilege
 Freeze the scene of the crime – do not contaminate or change

15. Using the Evidence:
Criminal and Civil Proceedings
 Criminal prosecutors
 Civil litigation attorneys – harassment, discrimination,
embezzlement, divorce
 Insurance companies
 Computer forensics specialists to help corporations and
lawyers
 Law enforcement officials
 Individuals to sue a company
 Also defense attorneys, and “the bad guys”

16. Issues and Problems that could occur
 Computer Evidence MUST be
- Authentic: not tampered with
- Accurate: have high integrity
- Complete: no missing points
- Convincing: no holes
- Conform: rules and regulations
- Handle change: data may be volatile and time sensitive
- Handle technology changes: tapes to disks; MAC to PC
- Human readable: Binary to words

17. Legal tests
 Countries with a common law tradition
- UK, US, Possibly Canada, Australia, New Zealand
 Real evidence
- Comes from an inanimate object and can be examined by
the court
 Testimonial evidence
- Live witness when cross examined
 Hearsay
- Wiki entry “Hearsay in English law and Hearsay in United
States law, a legal principle concerning the admission of
evidence through repetition of out-of-court statements”
 Are the following admissible in court?
- Data mining results, emails, printed documents

18. Traditional Forensics vs Computer Forensics
 Traditional Forensics
- Materials tested and testing methods usually do not
change rapidly
- Blood, DNA, Drug, Explosive, Fabric
 Computer Forensics
- Material tested and testing methods may change rapidly
- We did not have web logs in back in 1990
- We did not have RAID storage in 1980

19. Types of Acquisition
 Static Acquisition
- Acquire data from the original media
- The data in the original media will not change
 Live Acquisition
- Acquire data while the system is running
- A second live acquisition will not be the same
 Will focus on static acquisition

20. Digital Evidence Storage Formats
 Raw formats
- Bit by bit copying of the data from the disk
- Many tools could be used
 Proprietary formats
- Vendors have special formats
 Standards
- XML based formats for digital evidence
- Digital Evidence Markup Language
(Funded by National Institute of Justice)
- Experts have argued that technologies that allow disparate law
enforcement jurisdictions to share crime-related information will greatly
facilitate fighting crime. One of these technologies is the Global Justice
XML Data Model (GJXDM).
- http://ncfs.ucf.edu/digital_evd.html

21. Acquisition Methods
 Disk to Image File
 Disk to Disk
 Logical acquisition
- Acquire only certain files if the disk is too large
 Sparse acquisition
- Similar to logical acquisition but also collects fragments
of unallocated (i.e. deleted) data

22. Compression Methods
 Compression methods are used for very large data storage
- E.g., Terabytes/Petabytes storage
 Lossy vs Lossless compression
- Lossless data compression is a class of data
compression algorithms that allows the exact original
data to be reconstructed from the compressed data. The
term lossless is in contrast to lossy data compression,
which only allows an approximation of the original data to
be reconstructed, in exchange for better compression
rates.

23. Contingency Planning
 Failure occurs during acquisition
- Recovery methods
 Make multiple copies
- At least 2 copies
 Encryption decryption techniques so that the evidence is not
corrupted