Digital Forensics

Digital Forensics

Dr. Bhavani ThuraisinghamThe University of Texas at Dallas

Lecture #1

August 20, 2010

Outline

Introduction Applications- Law enforcement, Human resources, Other

Services Benefits Using the evidence Conclusion

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

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

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 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

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

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

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

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

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

Services

Data Services- Seizure, Duplication and preservation, recovery

Document and Media- Document searched, Media conversion

Expert witness Service options Other 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

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

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 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

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.”

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

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

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

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

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- 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

Conclusion

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