Difference between pages "Encase image file format" and "Windows Application Compatibility"

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The Encase image file format is used by [[EnCase]] used to store various types of digital evidence e.g.
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{{expand}}
* disk image (physical bitstream of an acquired disk)
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* volume image
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* memory
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* logical files
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== sysmain.sdb ==
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System compatibility database.
  
The format is (reportedly) based on ASR Data's Expert Witness Compression Format [http://www.asrdata.com/SMART/whitepaper.html].
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== RecentFileCache.bcf ==
Currently there are 2 version of the format; version 1 is a closed format and was succeeded by version 2 in EnCase 7, for which a format specification is available, but requires registration.
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In Windows 7 the RecentFileCache.bcf file is stored in:
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<pre>
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C:\Windows\AppCompat\Programs\
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</pre>
  
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== Amcache.hve ==
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The Amcache.hve file is a [[Windows NT Registry File (REGF)]].
  
The media data can be stored in multiple evidence files, which are called segment files.
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In Windows 8 the Amcache.hve file is stored in:
Each segment file consist of multiple sections, which has a distinct section start definition containing a section type.
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<pre>
Up to EnCase 5 the segment file were limited to 2 GiB, due to the internal 31-bit file offset representation. This limitation was lifted by adding a base offset value in EnCase 6.
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C:\Windows\AppCompat\Programs\
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</pre>
  
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== AppCompatCache ==
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In Windows 2000 and XP:
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<pre>
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Key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\AppCompatibility
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</pre>
  
EnCase allows to store the data compressed either using a fast or best level of the deflate compression method.
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In Windows 2003 and later:
EnCase 7 no longer distinguishes between fast or best compression and just provides for either uncompressed or compressed.
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<pre>
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Key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\AppCompatCache
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</pre>
  
 
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== External Links ==
Besides digital evidence the evidence files, or segment files, contain a header containing case information.
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* [http://technet.microsoft.com/en-us/library/dd837644(v=ws.10).aspx Technet: Understanding Shims], by [[Microsoft]]
The case information which entails date and time of acquisition, an examiner's name, notes on the acquisition, and an optional password.
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* [http://msdn.microsoft.com/en-us/library/bb432182(v=vs.85).aspx MSDN: Application Compatibility Database], by [[Microsoft]]
* In EnCase 3 the case information header is stored in the "header" section, which is defined twice within the file and contain the same information.
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* [http://www.alex-ionescu.com/?p=39 Secrets of the Application Compatilibity Database (SDB) – Part 1], by [[Alex Ionescu]], May 20, 2007
* As of EnCase 4 an additional "header2" section was added. The "header" section now appears only once, but the new "header2" section twice.
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* [http://www.alex-ionescu.com/?p=40 Secrets of the Application Compatilibity Database (SDB) – Part 2], by [[Alex Ionescu]], May 21, 2007
 
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* [http://www.alex-ionescu.com/?p=41 Secrets of the Application Compatilibity Database (SDB) – Part 3], by [[Alex Ionescu]], May 26, 2007
 
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* [http://recxltd.blogspot.com/2012/04/windows-appcompat-research-notes-part-1.html Windows AppCompat Research Notes - Part 1], by Ollie, 28 April 2012
The format adds error detection by storing the data with checksums (Adler32), for both the metadata as the data blocks, which are by default 64 x 512 byte sectors (32 KiB).
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* [http://recxltd.blogspot.com/2012/05/windows-appcompat-research-notes-part-2.html Windows AppCompat Research Notes - Part 2], by Ollie, 4 May 2012
As of EnCase 5 the number of sectors per block (chunk) can vary.
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* [https://dl.mandiant.com/EE/library/Whitepaper_ShimCacheParser.pdf Leveraging the Application Compatibility Cache in Forensic Investigations], by [[Andrew Davis]], May 4, 2012
EnCase 3F introduced an "error2" section that it uses to record the location and number of bad sector chunks. The way it handles the sections it can't read is that those areas are filled with zero.
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* [http://journeyintoir.blogspot.ch/2013/12/revealing-recentfilecachebcf-file.html Revealing the RecentFileCache.bcf File], by [[Corey Harrell]], December 2, 2013
Then EnCase displays to the user the areas that could not be read when the image was acquired. The granularity of unreadable chunks appears to be 32K.
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* [http://journeyintoir.blogspot.ch/2013/12/revealing-program-compatibility.html Revealing Program Compatibility Assistant HKCU AppCompatFlags Registry Keys], by [[Corey Harrell]], December 17, 2013
As of EnCase 5 the granularity of unreadable chunks can vary.
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* [http://journeyintoir.blogspot.ch/2014/04/triaging-with-recentfilecachebcf-file.html Triaging with the RecentFileCache.bcf File], by [[Corey Harrell]], April 21, 2014
 
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EnCase 3 can store a one-way hash of the data. For a bitstream it does so by calculating e.g. a MD5 hash of the original media data and adds a hash section to the last of the segment file.
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As of EnCase 6 the option to store a SHA1 hash was added.
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EnCase 5 and later have the option to store '''single files''' into the EnCase Logical Evidence File (LEF) or EWF-L01.
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This format changed slightly in EnCase 6 and 7.
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In EnCase 7 the EWF format was succeeded by the EnCase Evidence File Format Version 2 (EWF2-EX01 and EWF2-LX01).
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EWF2-EX01 is at it's lower levels a different format then EWF-E01 and provides support for:
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* bzip2 compression
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* direct encryption (AES-256) of the section data
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The same features are added to the new logical evidence file format (EWF2-LX01) with the exception of encryption.
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EWF2-EX01, EWF2-LX01 are not backwards compatible with previous EnCase products.
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== See Also ==
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[[EnCase]]
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== External Links ==
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* [http://www.asrdata.com/SMART/whitepaper.html ASR Data's Expert Witness Compression Format], no longer available
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* [http://web.archive.org/web/20100905235827/http://www.asrdata.com/SMART/whitepaper.html Internet archive copy of: ASR Data's Expert Witness Compression Format]
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* [http://www.guidancesoftware.com/DocumentRegistration.aspx?did=1000018246 EnCase Evidence File Format Version 2], requires registration
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* [http://code.google.com/p/libewf/downloads/detail?name=Expert%20Witness%20Compression%20Format%20%28EWF%29.pdf Expert Witness Compression Format (EWF)].
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* [http://code.google.com/p/libewf/downloads/detail?name=Expert%20Witness%20Compression%20Format%202%20%28EWF2%29.pdf Expert Witness Compression Format (EWF) version 2].
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* [http://www.cfreds.nist.gov/v2/Basic_Mac_Image.html Sample image in EnCase, iLook, and dd format] - From the [[Computer Forensic Reference Data Sets]] Project
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[[Category:Forensics File Formats]]
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Latest revision as of 00:06, 9 July 2014

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sysmain.sdb

System compatibility database.

RecentFileCache.bcf

In Windows 7 the RecentFileCache.bcf file is stored in:

C:\Windows\AppCompat\Programs\

Amcache.hve

The Amcache.hve file is a Windows NT Registry File (REGF).

In Windows 8 the Amcache.hve file is stored in:

C:\Windows\AppCompat\Programs\

AppCompatCache

In Windows 2000 and XP:

Key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\AppCompatibility

In Windows 2003 and later:

Key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\AppCompatCache

External Links