Computer Forensics

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Computer Forensics

• CS 407
• MW 1030 1230
• Texts
• File System Forensic Analysis, Brian Carrier
• Windows Forensics Analysis, 2nd editiion, 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/

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More Texts Electronic Crime Scene
Investigation A Guide for First Responders,
Second Edition, http//www.ncjrs.gov/pdffiles1/n
ij/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
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Advanced Computer ForensicsA New
RealmResponsiblities Ethical Legal Technical

• Three Course Sequence
• File system Forensics
• Network Forensics
• Memory Forensics
• ACE Certification
• Preparation for CCE Certification, ISFCE

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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
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Syllabus
Week 6-7 Registry Analysis Registry
structure, system information, tracking user
activity MRUs, time lines, USB devices,
restore points FTKs 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
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Computer Forensics

• As in all endeavors
• Blame always falls some where.
• Rule
• Let it not be in your lap.

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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

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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.

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Today

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

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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

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Business Issues

• No interruption of business
• Know the policies of the business
• Sensitive to the business costs during an
  investigation

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Privacy Issues

• Rights of the suspect
• Liabilities of the investigator
• Public versus private storage of information
• Expectation of privacy

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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

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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

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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

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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)?

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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

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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

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Communications Intercept

• Acquisition contemporaneous with transmission
• Content
• Addressing information

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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

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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

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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

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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

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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

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Title III - Today

• NSA surveillance puts all in disarray

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NSLs

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

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Evidence

• Demonstrative
• Documentary
• Testimonial
• Circumstantial
• Hearsay

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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

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Documentary Evidence

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

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Testimonial Evidence

• A persons testimony
• Offered to prove the truth of the matter

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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

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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.

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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

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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.

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Computer Stored Business Records

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

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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

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Chain of Custody

• The evidence must be accounted for at all times
  after seizure
• Very prone to violation with digital evidence
• Cant 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