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Computer Forensics

Computer Forensics. CS 407 MW 10:30 – 12:30 Texts: File System Forensic Analysis , Brian Carrier Windows Forensics Analysis , 2 nd editiion , Harlan Carvey Supplementary Texts: Digital Evidence and Computer Crime , Eoghan Casey

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Computer Forensics

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  1. Computer Forensics • CS 407 • MW 10:30 – 12:30 • Texts: • File System Forensic Analysis, Brian Carrier • Windows Forensics Analysis, 2ndeditiion, Harlan Carvey • Supplementary Texts: • Digital Evidence and Computer Crime, Eoghan Casey • Guide to Computer Forensics and Investigations, Nelson, et al • Web site: ackler.csrl.sou.edu/

  2. More Texts: • Electronic Crime Scene Investigation: A Guide for First Responders, Second Edition, http://www.ncjrs.gov/pdffiles1/nij/187736.pdf Forensic Examination of Digital Evidence: A Guide for Law Enforcement Series, http://www.ncjrs.gov/pdffiles1/nij/199408.pdf Best Practices for Seizing Electronic Evidence V2 www.fletc.gov/training/programs/legal-division/downloads-articles-and -faqs/downloads/other/bestpractices.pdf/view

  3. Advanced Computer ForensicsA New RealmResponsiblities Ethical Legal Technical • Three Course Sequence • File system Forensics • Live Incident Response, • FTK , Crime Scene Exercise • ACE Certification • Preparation for CCE Certification, ISFCE

  4. Syllabus Week 1: Procedural, Legal and Ethical Principals of Computer Forensics Week 2: Imaging Hard Drives Media preparation for cloning, proving it is sterile Imaging tools Intro to dd, dcfldd, ddrescue FTK Imager Write blockers Tool validation test plans and test reports Week 3-5: Hard Drive and File System Structure Master Boot Record, Partition tables, Directories FAT, NTFS, ext2, ext3, IDE, ATAPI, Sata, SCSI Drives, Raid devices

  5. Syllabus Week 6-7: Registry Analysis Registry structure, system information, tracking user activity MRUs, time lines, USB devices, restore points FTK’s Registry Viewer, regedit, and regripper Week 8-9: Windows File Analysis Event logs, link files, setup logs, firewall logs File metadata, $I30 files, prefetch files Week 10: File Signature and data carving File structure and file signatures “File Extractor Pro”

  6. Computer Forensics • As in all endeavors: • “Blame always falls some where.” • Rule: • “Let it not be in your lap.”

  7. Computer Forensics • Discovery and recovery of digital evidence • Usually post facto • Sometimes real time • Types of forensic investigations • Liturgical • Going to court • Crimes, etc. • Non-Liturgical • Administrative adjudication • Industry

  8. Purpose • Prove or disprove criminal activity • Prove or disprove policy violation • Prove or disprove malicious behavior to or by the computer/user • If the evidence is there, the case is yours to lose with very little effort.

  9. Today • Ethical issues • Privacy issues • Evidence • Association of suspect with evidence • Chain of custody • Seizing electronic evidence

  10. Ethical issues • Evidence • All of it • Emphasis on exculpatory • Respect for suspects privacy and rights • Beware of collateral damage • Proper use of dual use technology • All tools can be used to commit crime • All procedures can be used to hide crime

  11. Business Issues • No interruption of business • Know the policies of the business • Sensitive to the business costs during an investigation

  12. Privacy Issues • Rights of the suspect • Liabilities of the investigator • Public versus private storage of information • Expectation of privacy

  13. Search and Seize • With and without a warrant • Not for the computer forensics expert • Residences • Private Sector-workplaces • Public Sector-workplaces • “In plain sight” issues

  14. Subpoenas • Person to testify • Present to the court computers, records, documents • Authentication issues • Record alteration • Usually for computer based business records • Often a snapshot of ongoing record keeping

  15. Search Warrants • Show up and take away • Court approved with probable cause • Good for computers • Records, etc. • Sneak & peek • Compelling reason • Notify within 7 – 45 days • For stored communications and records • Caution: third party information

  16. Electronic Storage • Any temporary or intermediate storage of a wire or electronic communication incidental to the electronic transmission of the communications • And backup for the restoration of the electronic communication service (not for future use)‏

  17. Wire Communications • Telephone communications mostly • Specifically the communication must contain the human voice • At any point from the point of origin to the point of reception • Must be on a wire somewhere • Wire communication in “temporary or incidental” electronic storage is covered by Title III • Causes confusion • Unopened voice mail is covered • Opened voice mail is not

  18. Electronic Communications • Internet communications mostly • Signs, signals, writing, images, sounds, data, or intelligence transmitted electronically • BUT does not include • Wire or oral communications • Tone-only paging device • Cannot be characterized as containing the human voice

  19. Communications Intercept • Acquisition contemporaneous with transmission • Content • Addressing information

  20. Electronic surveillance • Pen/Trap Statue • Collection of addressing information for wire and electronic communications • Title III of the Omnibus Crime Control and Safe Streets Act of 1968 • Collection of content of wire and electronic communications

  21. Pen/Trap Statue • Collection of addressing information • Phone is different from Internet • Application for a Pen/Trap order • Who wants it • Where do they work • State their belief the info is relevant to an ongoing criminal investigation • Application is easy • Violation is severe

  22. Title III - 1968 • Assumption: any interception of private communication between two parties is illegal. • Title III order is required when • Intercepted communication is protected under Title III • The proposed surveillance is an interception oc communications • Is there a statutory exception

  23. Title III Wire Taps • Court approved upon probable cause • Feds need DoJ approval • Good for 30 days • Can apply for non-notification • Usually used for “wire communications” • Very dicey area between “wire communication” and “electronic communication”

  24. Title III - 2001 • Voice intercept authorized in computer hacking investigations • Electronic storage of wire communications is now covered by same rules as stored electronic communications (only need a search warrant)‏ • Session times, addresses only requires a subpoena not a Pen/Trap order • Warrants for e-mail are now nationwide

  25. Title III - Today • NSA surveillance puts all in disarray

  26. NSLs • Specifically enabled in the USA PATRIOT Act • Requires FBI supervisor approval • No judicial oversight • Disclosure is forbidden

  27. Evidence • Demonstrative • Documentary • Testimonial • Circumstantial • Hearsay

  28. Demonstrative Evidence • Physical evidence that one can see and inspect • Does not play a direct part in the incident • Of probative value • Sometimes referred to as real evidence

  29. Documentary Evidence • Evidence supplied by a writing or other document • Must be authenticated to be admissible

  30. Testimonial Evidence • A person’s testimony • Offered to prove the truth of the matter

  31. Hearsay Evidence • “Hearsay is a statement offered in evidence to prove the truth of the matter asserted” Federal Rules of Evidence, § 801 • There are many exceptions to hearsay evidence. • Most forensic evidence must be shown to be excepted from hearsay

  32. Computer Evidence • Two broad classes • Computer generated records • Computer stored records • Computer data contains potential hearsay evidence • To be admissible, a hearsay exception must be established • Unless it can be shown that the data are reliable, trustworthy, material and authentic.

  33. Computer Generated Data • Computer generated records • Data untouched by human hands. • Phone logs • ISP logs • syslogs • The data contains no hearsay evidence • To be admissible, it must be shown that the data are reliable, trustworthy, material and authentic. • Reliability of the computer programs

  34. Computer Stored Data • Computer stored records • Data potentially contains hearsay • Photo graphs • Results of Excel spreadsheets • A printout of an e-mail is considered to be an original. • However, to connect the e-mail to the defendant one must tie the computer system to the defendant. • The ISP records of the e-mail server are business records and only require testimony of the ISP.

  35. Computer Stored Business Records • Business records • Data generated in the usual course of business • Done regularly • A satisfies a hearsay exception.

  36. Evidence • Admissible • must be legally obtained and relevant • Reliable • has not been tainted (changed) since acquisition • Authentic • the real thing, not a replica • Complete • includes any exculpatory evidence • Believable • lawyers, judge & jury can understand it

  37. Chain of Custody • The evidence must be accounted for at all times after seizure • Very prone to violation with digital evidence • Can’t take it home to work on! • Sometimes it is hard to say where the evidence is. • Fortunately the courts accept hash codes • Not for long • MD5 collisions in less than a minute

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