Computer forensics (sometimes known as computer forensic science[1]) is a branch of digital forensic science pertaining to legal 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 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 becoming widely accepted as reliable within US and European court systems.
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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 hacking). The discipline of computer forensics emerged during this time as a method to recover and investigate digital evidence for use in court. Today it is used to investigate a wide variety of crime, including child pornography, fraud, 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), an electronic document (e.g. an email message or JPEG image).[2] 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".[3] 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.
In court computer forensic evidence is subject to the usual requirements for digital evidence; requiring information to be authentic, reliably obtained and admissible. Different countries have specific guidelines and practices for the recovery of evidence. In the United Kingdom examiners often follow guidelines from the Association of Chief Police Officers which help ensure the authenticity and integrity of evidence. While the guidelines are voluntary they are widely accepted in courts of Wales, England and Scotland.
Computer forensics has been used as evidence in criminal law since the mid 1980s, some notable examples include:[4]
Computer forensic investigations usually follow the standard digital forensic process (acquisition, analysis and reporting).[4] Investigations are performed on static data (i.e. acquired images) rather than "live" systems. This is a change from early forensic practices which, due to a lack of specialist tools, saw investigations commonly carried out on live data.
A number of techniques are used during computer forensics investigations.
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.[5] One application of "live analysis" is to recover RAM data (for example, using Microsoft's COFEE tool, windd, WindowsSCOPE) prior to removing an exhibit.
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 for which data recovery is possible is increased by low temperatures and higher cell voltages. Holding unpowered RAM below −60 °C will help preserve the residual data by an order of magnitude, thus improving the chances of successful recovery. However, it can be impractical to do this during a field examination.[10]
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.[4]
There are several computer forensics certifications available.
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