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Digital Forensics. Dr. Bhavani Thuraisingham The University of Texas at Dallas October 4, 2007. Outline. Introduction Applications Law enforcement, Human resources, Other Services Benefits Using the evidence Conclusion. Digital Forensics.

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Digital forensics

Digital Forensics

Dr. Bhavani Thuraisingham

The University of Texas at Dallas

October 4, 2007


  • Introduction

  • Applications

    • Law enforcement, Human resources, Other

  • Services

  • Benefits

  • Using the evidence

  • Conclusion

Digital forensics1
Digital Forensics

  • Digital forensics is about the investigation of crime including using digital/computer methods

  • More formally: “Digital forensics, also known as computer forensics, involved the preservation, identification, extraction, and documentation of computer evidence stored as data or magnetically encoded information”, by John Vacca

  • Digital evidence may be used to analyze cyber crime (e.g. Worms and virus), physical crime (e.g., homicide) or crime committed through the use of computers (e.g., child pornography)

Relationship to intrusion detection firewalls honeypots
Relationship to Intrusion Detection, Firewalls, Honeypots

  • They all work together with Digital forensics techniques

  • Intrusion detection

    • Techniques to detect network and host intrusions

  • Firewalls

    • Monitors traffic going to and from and organization

  • Honeypots

    • Set up to attract the hacker or enemy; Trap

  • Digital forensics

    • Once the attack has occurred or crime committed need to decide who committed the crime

Computer crime
Computer Crime

  • Computers are attacked – Cyber crime

    • Computer Virus

  • Computers are used to commit a crime

    • E.g., child predators, Embezzlement, Fraud

  • Computers are used to solve a crime

  • FBI’s workload: Recent survey

    • 74% of their efforts on white collar crimes such as healthcare fraud, financial fraud etc.

    • Remaining 26% of efforts spread across all other areas such as murder and child pornography

    • Source: 2003 Computer Crime and Security Survey, FBI

Objective and priority
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

Accuracy vs speed
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

The job of a forensics specialist
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?

Applications law enforcement
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?

Applications human resources
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

Applications other
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


  • Data Services

    • Seizure, Duplication and preservation, recovery

  • Document and Media

    • Document searched, Media conversion

  • Expert witness

  • Service options

  • Other services

Data services
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

Data services finding hidden data
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



Document and media services
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

Expert witness services
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?

Service options
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


    • 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.”

Other services
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

Benefits of using professional services
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

Using the evidence criminal and civil proceedings
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”

Issues and problems that could occur
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

Legal tests
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

Traditional forensics vs computer forensics
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


  • Important to have experts for computer forensics evidence gathering and analysis

  • Important to secure the evidence: authenticity, completeness, integrity

  • Important to have the proper tools for analysis

  • Important to apply the correct legal tests

  • Computer forencis can be used to benefit both the “good and bad guys”

  • Need to be several steps smarter than the enemy