Computer forensics

A forensic expert examining a mobile device that was seized during an investigation

Media types used for computer forensic analysis: a Fujifilm FinePix digital camera, two flash memory cards, a USB flash drive, a 5GB iPod, a CD-R or DVD recordable, and a Mini CD.

Computer forensics (also known as computer forensic science<ref name="noblett"/>) is a branch of digital forensic science pertaining to evidence found in computers and digital storage media. The goal of computer forensics is to examine digital media in a forensically sound manner with the aim of identifying, preserving, recovering, analyzing and presenting facts and opinions about the digital information.

Although it is most often associated with the investigation of a wide variety of computer crime, computer forensics may also be used in civil proceedings. The discipline involves similar techniques and principles to data recovery, but with additional guidelines and practices designed to create a legal audit trail.

Evidence from computer forensics investigations is usually subjected to the same guidelines and practices of other digital evidence. It has been used in a number of high-profile cases and is accepted as reliable within U.S. and European court systems.

Overview

In the early 1980s, personal computers became more accessible to consumers, leading to their increased use in criminal activity (for example, to help commit fraud). At the same time, several new "computer crimes" were recognized (such as cracking). The discipline of computer forensics emerged during this time as a method to recover and investigate digital evidence for use in court. Since then, computer crime and computer-related crime has grown, with the FBI reporting a suspected 791,790 internet crimes alone in 2020, a 69% increase over the amount reported in 2019.<ref>"2020 Internet Crime Report" (PDF).</ref><ref>"IC3 Releases 2020 Internet Crime Report". Federal Bureau of Investigation. Retrieved 2023-03-17.</ref> Today, computer forensics is used to investigate a wide variety of crime, including child pornography, fraud, espionage, cyberstalking, murder, and rape. The discipline also features in civil proceedings as a form of information gathering (for example, Electronic discovery)

Forensic techniques and expert knowledge are used to explain the current state of a digital artifact, such as a computer system, storage medium (e.g., hard disk or CD-ROM), or an electronic document (e.g., an email message or JPEG image).<ref name="cf-education"/> The scope of a forensic analysis can vary from simple information retrieval to reconstructing a series of events. In a 2002 book, Computer Forensics, authors Kruse and Heiser define computer forensics as involving "the preservation, identification, extraction, documentation and interpretation of computer data".<ref name="kruse" /> They go on to describe the discipline as "more of an art than a science", indicating that forensic methodology is backed by flexibility and extensive domain knowledge. However, while several methods can be used to extract evidence from a given computer, the strategies used by law enforcement are fairly rigid and lack the flexibility found in the civilian world.<ref name=gunsch />

Cybersecurity

Computer forensics is often confused with cybersecurity. Cybersecurity is about prevention and protection, while computer forensics is more reactionary and active, involving activities such as tracking and exposing. System security usually encompasses two teams, cybersecurity and computer forensics, which work together. A cybersecurity team creates systems and programs to protect data; if these fail, then the computer forensics team recovers the data and performs the investigation into the intrusion and theft. Both areas require knowledge of computer science.<ref>"What Is Computer Forensics?". Western Governors University. Retrieved 2022-03-04.</ref>

Computer-related crimes

Computer forensics are used to convict those involved in physical and digital crimes. Some of these computer-related crimes include interruption, interception, copyright infringement, and fabrication. Interruption relates to the destruction and stealing of computer parts and digital files. Interception is the unauthorized access of files and information stored on technological devices.<ref>Kruse II, Warren G.; Heiser, Jay G. (2001-09-26). Computer Forensics: Incident Response Essentials. Pearson Education. ISBN 978-0-672-33408-5.</ref> Copyright Infringement is using, reproducing, and distributing copyrighted information, including software piracy. Fabrication is accusing someone of using false data and information put in the system through an unauthorized source. Examples of interceptions are the Bank NSP case, Sony.Sambandh.com case, and business email compromise scams.<ref>Sabry, Fouad (2022-07-10). Digital Forensics: How digital forensics is helping to bring the work of crime scene investigating into the real world. One Billion Knowledgeable.</ref>

Use as evidence

In court, computer forensic evidence is subject to the usual requirements for digital evidence. This requires that information be authentic, reliably obtained, and admissible.<ref name="theadam" /> Different countries have specific guidelines and practices for evidence recovery. In the United Kingdom, examiners often follow Association of Chief Police Officers guidelines that help ensure the authenticity and integrity of evidence. While voluntary, the guidelines are widely accepted in British courts.

Computer forensics has been used as evidence in criminal law since the mid-1980s, some notable examples include:<ref name="casey" />

• BTK Killer: Dennis Rader was convicted of a string of serial killings that occurred over a period of sixteen years. Towards the end of this period, Rader sent letters to the police on a floppy disk.<ref>"The Capture of Serial Killer Dennis Rader, BTK | Psychology Today South Africa". www.psychologytoday.com. Retrieved 2023-03-17.</ref> Metadata within the documents implicated an author named "Dennis" at "Christ Lutheran Church"; this evidence helped lead to Rader's arrest.<ref>Dooley, Sean (January 22, 2019). "BTK serial killer's daughter: 'We were living our normal life. ... Then everything upended on us'". ABC News. Retrieved 2023-03-17.</ref>
• Joseph Edward Duncan: A spreadsheet recovered from Duncan's computer contained evidence that showed him planning his crimes. Prosecutors used this to show premeditation and secure the death penalty.<ref name="handbook" />
• Sharon Lopatka: Hundreds of emails on Lopatka's computer lead investigators to her killer, Robert Glass.<ref name="casey" />
• Corcoran Group: This case confirmed parties' duties to preserve digital evidence when litigation has commenced or is reasonably anticipated. Hard drives were analyzed by a computer forensics expert who could not find relevant emails the Defendants should have had. Though the expert found no evidence of deletion on the hard drives, evidence came out that the defendants were found to have intentionally destroyed emails, and misled and failed to disclose material facts to the plaintiffs and the court.
• Dr. Conrad Murray: Dr. Conrad Murray, the doctor of the deceased Michael Jackson, was convicted partially by digital evidence on his computer. This evidence included medical documentation showing lethal amounts of propofol.

Forensic process

Main article: Digital forensic process

A portable Tableau write blocker attached to a Hard Drive

Computer forensic investigations usually follow the standard digital forensic process or phases: acquisition, examination, analysis, and reporting. Investigations are performed on static data (i.e. acquired images) rather than "live" systems. This is a change from early forensic practices where a lack of specialist tools led to investigators commonly working on live data.

Computer forensics lab

The computer forensic lab is a safe and protected zone where electronic data can be managed, preserved, and accessed in a controlled environment. There, there is a very much reduced risk of damage or modification to the evidence. Computer forensic examiners have the resources needed to elicit meaningful data from the devices that they are examining.<ref>"Chapter 3: Computer Forensic Fundamentals - Investigative Computer Forensics: The Practical Guide for Lawyers, Accountants, Investigators, and Business Executives [Book]". www.oreilly.com. Retrieved 2022-03-04.</ref>

Techniques

A number of techniques are used during computer forensics investigations, and these include the following:

Cross-drive analysis

This is a forensic technique that correlates information found on multiple hard drives, and has been used to identify social networks and perform anomaly detection.<ref>Garfinkel, Simson L. (2006-09-01). "Forensic feature extraction and cross-drive analysis". Digital Investigation. The Proceedings of the 6th Annual Digital Forensic Research Workshop (DFRWS '06). 3: 71–81. doi:10.1016/j.diin.2006.06.007. ISSN 1742-2876.</ref><ref name="nsf" /><ref>David, Anne; Morris, Sarah; Appleby-Thomas, Gareth (2020-08-20). "A Two-Stage Model for Social Network Investigations in Digital Forensics" (PDF). Journal of Digital Forensics, Security and Law. 15 (2). doi:10.15394/jdfsl.2020.1667. ISSN 1558-7223. S2CID 221692362.</ref>

Live analysis

The examination of computers from within the operating system using custom forensics or existing sysadmin tools to extract evidence. The practice is useful when dealing with Encrypting File Systems, for example, where the encryption keys may be collected and, in some instances, the logical hard drive volume may be imaged (known as a live acquisition) before the computer is shut down. This process is also useful when dealing with multiple systems, for example as part of a network, or where the physical devices are not accessible, such as those running in the cloud. <ref> https://espace.curtin.edu.au/bitstream/handle/20.500.11937/93974/Adams%20RB%202023%20Public.pdf?sequence=1&isAllowed=y </ref>

Deleted files

A common technique used in computer forensics is the recovery of deleted files. Modern forensic software have their own tools for recovering or carving out deleted data.<ref name="exposed" /> Most operating systems and file systems do not always erase physical file data, allowing investigators to reconstruct it from the physical disk sectors. File carving involves searching for known file headers within the disk image and reconstructing deleted materials.

Stochastic forensics

A method which uses stochastic properties of the computer system to investigate activities lacking digital artifacts. Its chief use is to investigate data theft.

Steganography

One of the techniques used to hide data is via steganography, the process of hiding data inside of a picture or digital image. An example would be to hide pornographic images of children or other information that a given criminal does not want to have discovered. Computer forensics professionals can fight this by looking at the hash of the file and comparing it to the original image (if available.) While the images appear identical upon visual inspection, the hash changes as the data changes.<ref name=dunbar />

Mobile device forensics

Phone Logs: Phone companies usually keep logs of calls received, which can be helpful when creating timelines and gathering the locations of persons when the crime occurred.<ref name=":02">Pollard, Carol (2008). Computer Forensics for Dummies. John Wiley & Sons, Incorporated. pp. 219–230. ISBN 9780470434956.</ref>

Contacts: Contact lists help narrow down the suspect pool due to their connections with the victim or suspect.<ref name=":02" />

Text messages: Messages contain timestamps and remain in company servers indefinitely, even if deleted on the original device. Because of this, messages act as crucial records of communication that can be used to convict suspects.<ref name=":02" />

Photos: Photos can be critical in either supporting or disproving alibis by displaying a location or scene along with a timestamp of when the photo was taken.<ref name=":02" />

Audio Recordings: Some victims might have been able to record pivotal moments of the struggle, like the voice of their attacker or extensive context of the situation.<ref name=":02" />

Volatile data

Volatile data is any data that is stored in memory, or exists in transit, that will be lost when the computer loses power or is turned off. Volatile data resides in registries, cache, and random access memory (RAM). The investigation of this volatile data is called "live forensics".

When seizing evidence, if the machine is still active, any information stored solely in RAM that is not recovered before powering down may be lost.<ref name="handbook" /> One application of "live analysis" is to recover RAM data (for example, using Microsoft's COFEE tool, WinDD, WindowsSCOPE) prior to removing an exhibit. CaptureGUARD Gateway bypasses Windows login for locked computers, allowing for the analysis and acquisition of physical memory on a locked computer.

RAM can be analyzed for prior content after power loss, because the electrical charge stored in the memory cells takes time to dissipate, an effect exploited by the cold boot attack. The length of time that data is recoverable is increased by low temperatures and higher cell voltages. Holding unpowered RAM below −60 °C helps preserve residual data by an order of magnitude, improving the chances of successful recovery. However, it can be impractical to do this during a field examination.<ref name="ColdBoot" />

Some of the tools needed to extract volatile data, however, require that a computer be in a forensic lab, both to maintain a legitimate chain of evidence, and to facilitate work on the machine. If necessary, law enforcement applies techniques to move a live, running desktop computer. These include a mouse jiggler, which moves the mouse rapidly in small movements and prevents the computer from going to sleep accidentally. Usually, an uninterruptible power supply (UPS) provides power during transit.

However, one of the easiest ways to capture data is by actually saving the RAM data to disk. Various file systems that have journaling features such as NTFS and ReiserFS keep a large portion of the RAM data on the main storage media during operation, and these page files can be reassembled to reconstruct what was in RAM at that time.<ref name=geiger />

Analysis tools

See also: List of digital forensics tools

A number of open source and commercial tools exist for computer forensics investigation. Typical forensic analysis includes a manual review of material on the media, reviewing the Windows registry for suspect information, discovering and cracking passwords, keyword searches for topics related to the crime, and extracting e-mail and pictures for review.<ref name="casey" /> Autopsy (software), Belkasoft Evidence Center, Forensic Toolkit (FTK), EnCase are the some of tools used in Digital forensics.

Jobs in computer forensics

Digital forensics analyst

A digital forensics analyst is responsible for preserving digital evidence, cataloging collected evidence, analyzing evidence in a manner relevant to the ongoing case, responding to cyber breaches (usually in a corporate context), writing reports containing findings, and testifying in court.<ref>"What Is a Digital Forensic Analyst?". EC Council. 2022-12-28. Archived from the original on 2022-11-28. Retrieved 2022-12-28.</ref> A digital forensic analyst may alternatively be referred to as a computer forensic analyst, digital forensic examiner, cyber forensic analyst, forensic technician, or other similarly named titles, although these roles perform the same duties.<ref>"CISA Cyber Defense Forensics Analyst". Cybersecurity & Infrastructure Security Agency (CISA). 2022-12-28. Archived from the original on 2022-11-05. Retrieved 2022-12-28.</ref>

Certifications

There are several computer forensics certifications available, such as the ISFCE Certified Computer Examiner, Digital Forensics Investigation Professional (DFIP) and IACRB Certified Computer Forensics Examiner.

The top vendor independent certification (especially within EU) is considered the CCFP - Certified Cyber Forensics Professional.<ref>"Cybersecurity Certification". isc2.org. Retrieved 2022-11-18.</ref><ref>"CCFP Salaries surveys". ITJobsWatch. Archived from the original on 2017-01-19. Retrieved 2017-06-15.</ref>

Others, worth to mention for USA or APAC are: The International Association of Computer Investigative Specialists offers the Certified Computer Examiner program.

The International Society of Forensic Computer Examiners offers the Certified Computer Examiner program.

Many commercial based forensic software companies are now also offering proprietary certifications on their products. For example, Guidance Software offering the (EnCE) certification on their tool EnCase, AccessData offering (ACE) certification on their tool FTK, PassMark Software offering certification on their tool OSForensics, and X-Ways Software Technology offering (X-PERT) certification for their software, X-Ways Forensics.<ref>"X-PERT Certification Program". X-pert.eu. Retrieved 2015-11-26.</ref>

See also

• Certified Computer Examiner
• Certified Forensic Computer Examiner
• Counter forensics
• Cryptanalysis
• Data remanence
• Disk encryption
• Encryption
• Hidden file and hidden directory
• Information technology audit
• MAC times
• Steganalysis
• United States v. Arnold

Further reading

• A Practice Guide to Computer Forensics, First Edition (Paperback) by David Benton (Author), Frank Grindstaff (Author)
• Casey, Eoghan; Stellatos, Gerasimos J. (2008). "The impact of full disk encryption on digital forensics". Operating Systems Review. 42 (3): 93–98. CiteSeerX 10.1.1.178.3917. doi:10.1145/1368506.1368519. S2CID 5793873.
• YiZhen Huang; YangJing Long (2008). "Demosaicking recognition with applications in digital photo authentication based on a quadratic pixel correlation model" (PDF). Proc. IEEE Conference on Computer Vision and Pattern Recognition: 1–8. Archived from the original (PDF) on 2010-06-17. Retrieved 2009-12-18.
• Incident Response and Computer Forensics, Second Edition (Paperback) by Chris Prosise (Author), Kevin Mandia (Author), Matt Pepe (Author) "Truth is stranger than fiction..." (more)
• Ross, S.; Gow, A. (1999). Digital archaeology? Rescuing Neglected or Damaged Data Resources (PDF). Bristol & London: British Library and Joint Information Systems Committee. ISBN 978-1-900508-51-3.
• George M. Mohay (2003). Computer and intrusion forensics. Artech House. p. 395. ISBN 978-1-58053-369-0.
• Chuck Easttom (2013). System Forensics, Investigation, and Response. Jones & Bartlett. p. 318. ISBN 978-1284031058. Archived from the original on 2013-06-14. Retrieved 2013-09-23.

Related journals

• IEEE Transactions on Information Forensics and Security
• Journal of Digital Forensics, Security and Law
• International Journal of Digital Crime and Forensics
• Journal of Digital Investigation
• International Journal of Digital Evidence
• International Journal of Forensic Computer Science
• Journal of Digital Forensic Practice
• Cryptologia
• Small Scale Digital Device Forensic Journal