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| − | {{expand}}
| + | [[Category:Anti-forensics tools]][[:Category:Anti-forensics tools|Anti-forensics]] |
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| − | Disk imaging is the process of making a bit-by-bit copy of a disk. Imaging (in more general terms) can apply to anything that can be considered as a bit-stream, e.g. a physical or logical volumes, network streams, etc.
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| − | The most straight-forward disk imaging method is reading a disk from start to end and writing the data to a [[:Category:Forensics_File_Formats|Forensics image format]].
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| − | This can be a time consuming process especially for disks with a large capacity.
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| − | == Disk Imaging Solutions ==
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| − | See: [[:Category:Disk Imaging|Disk Imaging Solutions]]
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| − | == Common practice ==
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| − | It common practice to use a [[Write Blockers|Write Blocker]] when imaging a pyhical disk. The write blocker is an additional measure to prevent write access to the disk.
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| − | Also see: [[DCO and HPA|Device Configuration Overlay (DCO) and Host Protected Area (HPA)]]
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| − | == Error tolerance and recovery ==
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| − | == Smart imaging ==
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| − | Smart imaging is a combination of techniques to make the imaging process more intelligent.
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| − | * Compressed storage
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| − | * Deduplication
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| − | * Selective imaging
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| − | * Decryption while imaging
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| − | === Compressed storage ===
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| − | A common technique to reduce the size of an image file is to compress the data.
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| − | On modern computers, with multiple cores, the compression can be done in parallel reducing the output without prolonging the imaging process.
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| − | Since the write speed of the target disk can be a bottleneck in imaging process, parallel compression can reduce the total time of the imaging process.
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| − | [[Guymager]] was one of the first imaging tools to implement the concept of multi-process compression for the [[Encase image file format]]. This technique is now used by various imaging tools including [http://www.tableau.com/index.php?pageid=products&model=TSW-TIM Tableau Imager (TIM)]
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| − | Other techniques like storing the data sparse or '''empty-block compression''' can reduce the total time of the imaging process and the resulting size of new non-encrypted (0-byte filled) disks.
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| − | === Deduplication ===
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| − | Deduplication is the process of determining and storing data that occurs more than once on-disk, only once in the image.
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| − | It is even possible to store the data once for a corpus of images using techniques like hash based imaging.
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| − | === Selective imaging ===
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| − | Selective imaging is a technique to only make a copy of certain information on a disk like the $MFT on an [[NTFS]] volume with the necessary contextual information.
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| − | [[EnCase]] Logical Evidence Format (LEF) is an example of a selective image; although only file related contextual information is stored in the format by [[EnCase]].
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| − | === Decryption while imaging ===
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| − | Encrypted data is worst-case scenario for compression. Because the encryption process should be deterministic a solution to reduce the size of an encrypted image is to store it non-encrypted and compressed and encrypt it on-the-fly if required. Although this should be rare since the non-encrypted data is what undergoes analysis.
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| − | == Also see ==
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| − | * [[:Category:Forensics_File_Formats|Forensics File Formats]]
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| − | * [[Write Blockers]]
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| − | == External Links ==
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| − | * [http://www.tableau.com/pdf/en/Tableau_Forensic_Disk_Perf.pdf Benchmarking Hard Disk Duplication Performance in Forensic Applications], by [[Robert Botchek]]
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| − | === Hash based imaging ===
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| − | * [http://www.dfrws.org/2010/proceedings/2010-314.pdf Hash based disk imaging using AFF4], by [[Michael Cohen]], [[Bradley Schatz]]
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| − | [[Category:Disk Imaging]]
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