Computer Forensics
description
Transcript of Computer Forensics
Computer Forensics CS 407 MW 10:30 – 12:30 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/
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 V2www.fletc.gov/training/programs/legal-division/downloads-
articles-and -faqs/downloads/other/bestpractices.pdf/view
Advanced Computer ForensicsA New Realm
Responsiblities Ethical
LegalTechnical
Three Course Sequence1. File system Forensics2. Network Forensics 3. Memory Forensics
ACE Certification Preparation for CCE Certification, ISFCE
Syllabus
Week 1: Procedural, Legal and Ethical Principals of Computer Forensics
Week 2: Imaging Hard DrivesMedia preparation for cloning, proving it is sterileImaging toolsIntro to dd, dcfldd, ddrescue FTK ImagerWrite blockersTool validation test plans and test reports
Week 3-5: Hard Drive and File System Structure
Master Boot Record, Partition tables, DirectoriesFAT, NTFS, ext2, ext3,IDE, ATAPI, Sata, SCSI Drives, Raid devices
Syllabus
Week 6-7: Registry AnalysisRegistry structure, system information, tracking user activityMRUs, time lines, USB devices, restore pointsFTK’s Registry Viewer, regedit, and regripper
Week 8-9: Windows File Analysis
Event logs, link files, setup logs, firewall logsFile metadata, $I30 files, prefetch files
Week 10: File Signature and data carving
File structure and file signatures“File Extractor Pro”
Computer Forensics As in all endeavors:
“Blame always falls some where.”
Rule:“Let it not be in your lap.”
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
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.
Today Ethical issues Privacy issues Evidence Association of suspect with evidence Chain of custody Seizing electronic evidence
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
Business Issues No interruption of business Know the policies of the business Sensitive to the business costs during an
investigation
Privacy Issues Rights of the suspect Liabilities of the investigator Public versus private storage of information Expectation of privacy
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
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
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
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)
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
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
Communications Intercept Acquisition contemporaneous with transmission
Content Addressing information
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
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
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
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”
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
Title III - Today NSA surveillance puts all in disarray
NSLs Specifically enabled in the USA PATRIOT Act Requires FBI supervisor approval No judicial oversight Disclosure is forbidden
Evidence Demonstrative Documentary Testimonial Circumstantial Hearsay
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
Documentary Evidence Evidence supplied by a writing or other
document Must be authenticated to be admissible
Testimonial Evidence A person’s testimony Offered to prove the truth of the matter
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
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.
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
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.
Computer Stored Business Records
Business records Data generated in the usual course of business Done regularly
A satisfies a hearsay exception.
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
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