Digital forensic process: Difference between revisions

Revision as of 16:41, 10 September 2017

Revision as of 04:18, 22 September 2017

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==Personnel==

The stages of the digital forensics process require differingdifferent specialist training and knowledge,. thereThere are two rough levels of personnel:<ref name="casey" />

;Digital forensic technician

:Technicians may gather or process evidence at crime scenes,. inThese thetechnicians fieldare of digital forensics training is neededtrained on the correct handling of technology (for example how to preserve the evidence). Technicians may be required to carry out "Live analysis" of evidence. - variousVarious tools to simplify this procedure have been produced, most notably [[Microsoft]]'s [[COFEE]].

;Digital Evidence Examiners

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There have been many attempts to develop a process model but so far none have been universally accepted. Part of the reason for this may be due to the fact that many of the process models were designed for a specific environment, such as law enforcement, and they therefore could not be readily applied in other environments such as incident response.<ref name="adams" /> This is a list of the main models since 2001 in chronological order:<ref name="adams" />

* The SystematicAbstract Digital Forensic Investigation Model (SRDFIM) (AgarwalReith, et al., 20112002)

* The AbstractIntegrated Digital ForensicInvestigative ModelProcess (Reith,Carrier et& al.Spafford, 20022003)

* An Extended Model of Cybercrime Investigations (Ciardhuain, 2004)

* The IntegratedEnhanced Digital InvestigativeInvestigation Process Model (CarrierBaryamureeba & SpaffordTushabe, 20032004)

* The Digital Crime Scene Analysis Model (Rogers, 2004)

An* ExtendedA ModelHierarchical, ofObjectives-Based CybercrimeFramework for the Digital Investigations Process (CiardhuainBeebe & Clark, 2004)

* Framework for a Digital Investigation (Kohn, et al., 2006)

* The EnhancedFour DigitalStep InvestigationForensic Process Model (BaryamureebaKent, &et Tushabeal., 20042006)

* FORZA - Digital forensics investigation framework (Ieong, 2006)

* Process Flows for Cyber Forensics Training and Operations (Venter, 2006)

The Digital Crime Scene Analysis Model (Rogers, 2004)

* The Common Process Model (Freiling & Schwittay, (2007)

* The Two-Dimensional Evidence Reliability Amplification Process Model (Khatir, et al., 2008)

A Hierarchical, Objectives-Based Framework for the Digital Investigations Process (Beebe & Clark, 2004)

* The Digital Forensic Investigations Framework (Selamat, et al., 2008)

Framework* forThe aSystematic Digital Forensic Investigation Model (SRDFIM) (KohnAgarwal, et al., 20062011)

* The Advanced Data Acquisition Model (ADAM): A process model for digital forensic practice (Adams, 2012)

The Four Step Forensic Process (Kent, et al., 2006)

FORZA - Digital forensics investigation framework (Ieong, 2006)

Process Flows for Cyber Forensics Training and Operations (Venter, 2006)

The Common Process Model (Freiling & Schwittay, (2007)

The Two-Dimensional Evidence Reliability Amplification Process Model (Khatir, et al., 2008)

The Digital Forensic Investigations Framework (Selamat, et al., 2008)

The Systematic Digital Forensic Investigation Model (SRDFIM) (Agarwal, et al., 2011)

The Advanced Data Acquisition Model (ADAM): A process model for digital forensic practice (Adams, 2012)

==Seizure==

Prior to the actual examination, digital media will be seized. In criminal cases this will often be performed by [[Law enforcement agency|law enforcement]] personnel trained as technicians to ensure the preservation of evidence. In civil matters it will usually be a company officer, often untrained. Various laws cover the [http://www.duhaime.org/LegalDictionary/S/Seizure.aspx seizure] of material. In criminal matters, law related to [[search warrants]] is applicable. In civil proceedings, the assumption is that a company is able to investigate their own equipment without a warrant, so long as the privacy and human rights of employees are observed.

==Acquisition==

[[File:Tableau TD3 Forensic Imager 2014-06-26 07-05.jpg|thumb|Example of a portable disk imaging device]]

Once exhibits have been seized, an exact [[Disk sector|sector]] level duplicate (or "forensic duplicate") of the media is created, usually via a [[Forensic disk controller|write blocking]] device,. aThe duplication process is referred to as ''[[Disk imaging#Hard drive imaging|Imaging]]'' or ''Acquisition''.<ref name="horenbeeck"/> The duplicate is created using a hard-drive duplicator or software imaging tools such as [[DCFLdd]], [[IXimager]], [[Guymager]], TrueBack, [[EnCase]], [[Forensic Toolkit|FTK]] Imager or FDAS. The original drive is then returned to secure storage to prevent tampering.

The acquired image is verified by using the [[SHA-1]] or [[MD5]] [[cryptographic hash function|hash function]]s. At critical points throughout the analysis, the media is verified again, known as "hashing", to ensure that the evidence is still in its original state.

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After acquisition the contents of (the HDD) image files are analysed to identify evidence that either supports or contradicts a hypothesis or for signs of tampering (to hide data).<ref name="carrier" /> In 2002 the ''International Journal of Digital Evidence'' referred to this stage as "an in-depth systematic search of evidence related to the suspected crime".<ref name="ijde-2002" /> By contrast Brian Carrier, in 2006, describes a more "intuitive procedure" in which obvious evidence is first identified after which "exhaustive searches are conducted to start filling in the holes"<ref name="df-basics"/>

During the analysis an investigator usually recovers evidence material using a number of different methodologies (and tools), often beginning with recovery of deleted material. Examiners use specialist tools (EnCase, ILOOKIX, FTK, etc.) to aid with viewing and recovering data. The type of data recovered varies depending on the investigation;, but examples include email, chat logs, images, internet history or documents. The data can be recovered from accessible disk space, deleted (unallocated) space or from within operating system cache files.<ref name="casey" />

Various types of techniques are used to recover evidence, usually involving some form of keyword searching within the acquired image file;, either to identify matches to relevant phrases or to parsefilter out known file types. Certain files (such as graphic images) have a specific set of bytes which identify the start and end of a file,. ifIf identified, a deleted file can be reconstructed.<ref name="casey" /> Many forensic tools use [[Cryptographic hash function|hash signatures]] to identify notable files or to exclude known (benign) onesfiles; acquired data is hashed and compared to pre-compiled lists such as the ''Reference Data Set'' (RDS) from the [[National Software Reference Library]]<ref name="horenbeeck" />

On most media types, including standard magnetic hard disks, once data has been [[Secure file deletion|securely deleted]] it can never be recovered.<ref>{{cite web

| url = http://www.anti-forensics.com/disk-wiping-one-pass-is-enough

| title = Disk Wiping – One Pass is Enough

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}}</ref>

Once evidence is recovered the information is analysed to reconstruct events or actions and to reach conclusions, work that can often be performed by less specialistspecialized staff.<ref name="ijde-2002" /> Digital investigators, particularly in criminal investigations, have to ensure that conclusions are based upon data and their own expert knowledge.<ref name="casey" /> In the US, for example, Federal Rules of Evidence state that a qualified expert may testify “in the form of an opinion or otherwise” so long as:

{{quote|(1) the testimony is based upon sufficient facts or data, (2) the testimony is the product of reliable principles and methods, and (3) the witness has applied the principles and methods reliably to the facts of the case.<ref name="rule702" />}}

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When an investigation is completed the information is often reported in a form suitable for [[layman|non-technical individuals]]. Reports may also include audit information and other meta-documentation.<ref name="casey"/>

When completed, reports are usually passed to those commissioning the investigation, such as law enforcement (for criminal cases) or the employing company (in civil cases), who will then decide whether to use the evidence in court. Generally, for a criminal court, the report package will consist of a written expert conclusion of the evidence as well as the evidence itself (often presented on digital media).<ref name="casey"/>

==References==