Difference between pages "Kristinn Gudjonsson" and "Disk Imaging"

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[[Kristinn Gudjonsson]] Skyggnir Kristinn GuTHjonsson is the team leader of information security at Skyggnir, one of Iceland's largest hosting providers. Daily responsibilities include computer forensics, incident handling and response, intrusion analysis and security audits of networks and servers.
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Kristinn holds a M.Sc. degree in computer engineering from INT (Institut National des Telecommunications) in Paris as well as a B.Sc. degree in electrical and computer engineering from the University of Iceland. Kristinn also holds several certifications such as GCIA (GIAC Certified Incident Analyst), GCIH (GIAC Certified Incident Handler), GCFA (GIAC Certified Forensic Analyst) as well as certifications from vendors, such as CISP (Cisco Ironport Security Professional) and others.
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Kristinn is a member of the SANS advisory board as well as being a local mentor for the institution. He has also taught courses in both University of Reykjavik and University of Iceland in information security as well as regularly giving seminars to increase security awareness among employees of various companies in Iceland. Kristinn writes blogs about computer forensics and incident response, which can be read at his IR and Forensics Talk Blog as well as on the SANS computer forensics blog. He is also the author and creator of the tool log2timeline, an open-source artifact timeline creation and analysis tool.
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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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== 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.
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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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== 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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* Deduplication
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* Selective imaging
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* Decryption while imaging
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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.
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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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== 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]]

Revision as of 07:15, 21 July 2012

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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.

The most straight-forward disk imaging method is reading a disk from start to end and writing the data to a Forensics image format. This can be a time consuming process especially for disks with a large capacity.

Compressed storage

A common technique to reduce the size of an image file is to compress the data. On modern computers, with multiple cores, the compression can be done in parallel reducing the output without prolonging the imaging process. 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. Guymager was one of the first imaging tools to implement the concept of multi-process compression.

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.

Error tolerance and recovery

Smart imaging

Smart imaging is a combination of techniques to make the imaging process more intelligent.

  • Deduplication
  • Selective imaging
  • Decryption while imaging

Deduplication

Deduplication is the process of determining and storing data that occurs more than once on-disk, only once in the image. It is even possible to store the data once for a corpus of images using techniques like hash based imaging.

Selective imaging

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.

EnCase Logical Evidence Format (LEF) is an example of a selective image.

Decryption while imaging

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.

Also see

Forensics File Formats

External Links

Hash based imaging