Difference between pages "New Technology File System (NTFS)" and "AFF"

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The '''New Technology File System''' ('''NTFS''') is a [[file system]] developed and introduced by [[Microsoft]] in 1995 with [[Windows]] NT. As a replacement for the [[FAT]] file system, it quickly became the standard for [[Windows 2000]], [[Windows XP]] and [[Windows Server 2003]].
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The '''Advanced Forensics Format''' ('''AFF''') is an extensible open format for the storage of [[disk image]]s and related forensic [[metadata]]. It was originally developed by [[Simson Garfinkel]] and [[Basis Technology]]. The last version of AFF is implemented in the [[AFFLIBv3]] library, which can be found on [https://github.com/simsong/AFFLIBv3 github].  [[AFF4]] builds upon many of the concepts developed in AFF.  AFF4 was developed by [[Michael Cohen]], Simson Garfinkel and Bradley Schatz. That version can be downloaded from [https://code.google.com/p/aff4/ Google Code].
  
The features of NTFS include:
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'''AFFLIBv3 has been depreciated and should not be used for new projects.'''
  
* [[Hard-links]]
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[[Sleuthkit]], [[Autopsy]] , [[OSFMount]], [[Xmount]], [[FTK Imager]] and [[FTK]] support the AFFv3 image format.
* Improved performance, reliability and disk space utilization
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* Security [[access control lists]]
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* File system journaling
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== Time Stamps ==
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==AFF Background==
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AFF was created to be an open and extensible file format to store disk images and associated metadata. The goal was to create a disk imaging format that would not lock users into a proprietary format that may limit how he or she may analyze it. An open standard enables investigators to quickly and efficiently use their preferred tools to solve crimes, gather intelligence, and resolve security incidents. The format was implemented in AFFLIB which was distributed with an open source license.
  
NTFS keeps track of lots of time stamps. Each file has a time stamp for 'Create', 'Modify', 'Access', and 'Entry Modified'. The latter refers to the time when the MFT entry itself was modified. These four values are commonly abbreviated as the 'MACE' values. Note that other attributes in each MFT record may also contain timestamps that are of forensic value.
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After AFFLIB was published, [[Joachim Metz]] published [[libewf]], an open source implementation of the EnCase Expert Witness format. Later, Guidance Software modified its format to allow single disk volumes larger than 4GiB. Together these two changes significantly decreased the need for AFF and AFFLIB.
  
Additional information on how NTFS timestamps work when files are moved or copied is available here: [http://support.microsoft.com/kb/299648 Microsoft KB 299648]
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In 2009 Cohen, Garfinkel and Schatz published an article on AFF4, a new file format that incorporated and expanded on the underlying AFF ideas. AFF4 provides for multiple data views within a single data archives and allows links between archives. As a result, AFF4 natively supports selective imaging, logical file volumes, hash-based imaging, and a variety of case-management scenarios.
  
=== Changes in Windows Vista  ===
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==AFFv3 Extensions==
In Windows Vista, NTFS no longer tracks the Last Access time of a file by default. This feature can be enabled by setting the NtfsDisableLastAccessUpdate value to '0' in the Registry key:
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<pre>HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\FileSystem</pre>
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Note that this feature has been around since as early as Windows 2000 [http://technet.microsoft.com/en-us/library/cc959914.aspx].
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The original AFF format is a single file that contains segments with drive data and metadata. Its contents can be compressed, but it can be quite large as the data on modern hard disks often reach 100GB in size.
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AFFv3 supported three file extensions --– AFF, AFD and AFM –-- and provided a tool to easily convert between the variations.
  
== Alternate Data Streams ==
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For ease of transfer, large AFF files can be broken into multiple AFD format files. The smaller AFD files can be readily moved around a FAT32 file system which limits files to 2GB or stored on DVDs, which have similar size restrictions. The AFM format stores the metadata in an AFF file, and the disk data in a separate raw file. This format allows analysis tools that support the raw format to access the data, but without losing the metadata.
The '''NTFS''' file system includes a feature referred to as Alternate Data Streams (ADSs). This feature has also been referred to as "multiple data streams", "alternative data streams", etc.  ADSs were included in '''NTFS''' in order to support the resource forks employed by the Hierarchal File System ([[HFS]]) employed by Macintosh systems.
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As of [[Windows XP]] SP2, files downloaded via Internet Explorer, Outlook, and Windows Messenger were automatically given specific "zoneid" ADSs. The [[Windows]] Explorer shell would then display a warning when the user attempted to execute these files (by double-clicking them).
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===Compression and Encryption===
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AFF supports two compression algorithms: zlib, which is fast and reasonably efficient, and LZMA, which is slower but dramatically more efficient. zlib is the same compression algorithm used by EnCase. As a result, AFF files compressed with zlib are roughly the same size as the equivalent EnCase file. AFF files can be recompressed using the LZMA algorithm. These files are anywhere from 1/2 to 1/10th the size of the original AFF/EnCase file.
  
Sysadmins should be aware that prior to Vista, there are no tools native to the [[Windows]] platform that would allow you to view the existence of arbitrary ADSs. While ADSs can be created and their contents executed or viewed, it wasn't until the "/r" switch was introduced with the "dir" command on Vista that arbitrary ADSs would be visible. Prior to this, tools such as [http://www.heysoft.de/Frames/f_sw_la_en.htm LADS] could be used to view the existence of these files.
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AFF2.0 supports encryption of disk images. Unlike the password implemented by EnCase, encrypted images cannot be accessed without the necessary encryption key. FTK Imager/FTK added support for this encryption in version 3.0 and are able to create and access AFF encrypted images.
  
Microsoft FSRM (File System Resource Manager) also uses ADS as part of 'file classification'.
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=== AFFLIBv3 Tools ===
  
Examiners should be aware that most forensic analysis applications, including [[EnCase]] and ProDiscover, will display ADSs found in acquired images in red.
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* [[aimage]]
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* [[ident]]
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* [[afcat]]
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* [[afcompare]]
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* [[afconvert]]
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* [[affix]]
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* [[affuse]]
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* [[afinfo]]
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* [[afstats]]
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* [[afxml]]
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* [[afsegment]]
  
== Advanced Format (4KB Sector) Hard Drives ==
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= See Also =
NTFS does not natively handle drives that use the new standard of 4KB sectors. For information on this, see [[Advanced Format]].
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== Transactional NTFS (TxF) ==
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* [[AFF Developers Guide]] --- A guide for programmers on how to use the AFF
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* [[AFF Development Task List]] --- Want to help with AFF? Here is a list of things that need to be done.
  
According to MSDN Transactional NTFS (TxF) allows file operations on an NTFS file system volume to be performed in a transaction.  
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== External Links ==
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* [http://www.basistech.com/digital-forensics/aff.html Basis Technology's AFF website]
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* [http://www.osforensics.com/tools/mount-disk-images.html OSFMount - 3rd party tool for mounting AFF disk images with a drive letter]
  
Several TxF related file-system-metadata files can be found in the file-system-metadata directory: \$Extend\$RmMetadata\. TxF also uses the MFT attribute $LOGGING_UTILITY_STREAM with the name $TXF_DATA.
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[[Category:Forensics File Formats]]
 
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[[Category:Open Source Tools]]
TxF uses the [[Common Log File System (CLFS)]]
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== External links ==
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* [http://technet.microsoft.com/en-us/library/cc781134%28WS.10%29.aspx Technet: How NTFS Works], by [[Microsoft]]
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* [http://en.wikipedia.org/wiki/NTFS Wikipedia: NTFS]
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* [http://msdn.microsoft.com/en-us/library/bb968806%28v=VS.85%29.aspx MSDN: Transactional NTFS]
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* [http://en.wikipedia.org/wiki/Transactional_NTFS Wikipedia: Transactional NTFS]
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* [http://www.tzworks.net/prototype_page.php?proto_id=12  Windows NTFS Metadata Extractor Utility] Free tool that can be run on Windows, Linux or Mac OS-X
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* [http://www.tzworks.net/prototype_page.php?proto_id=28 Graphic Engine for NTFS Analysis (gena)] (GUI to view NTFS internals/extract data on live systems)
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* [http://sourceforge.net/projects/linux-ntfs/files/NTFS%20Documentation/ Linux-ntfs Documentation] Detailed documentation of the NTFS format by the Linux-NTFS driver creators.
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* [http://support.microsoft.com/kb/140365 Default cluster size for NTFS, FAT, and exFAT]
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* [http://code.google.com/p/libfslibs/downloads/detail?name=New%20Technologies%20File%20System%20%28NTFS%29.pdf New Technologies File System (NTFS)], by the [[libfslibs|libfslibs project]], August 2009
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* [https://www.mandiant.com/blog/striking-gold-incident-response-ntfs-indx-buffers-part-1-extracting-indx/ Incident Response with NTFS INDX Buffers – Part 1: Extracting an INDX Attribute], by William Ballenthin, September 18, 2012
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* [https://www.mandiant.com/blog/incident-response-ntfs-indx-buffers-part-2-internal-structures-file-attribute/ Incident Response with NTFS INDX Buffers – Part 2: The Internal Structures of a File Name Attribute], by Jeff Hamm, September 26, 2012
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[[Category:File Systems]]
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Revision as of 12:18, 9 January 2014

The Advanced Forensics Format (AFF) is an extensible open format for the storage of disk images and related forensic metadata. It was originally developed by Simson Garfinkel and Basis Technology. The last version of AFF is implemented in the AFFLIBv3 library, which can be found on github. AFF4 builds upon many of the concepts developed in AFF. AFF4 was developed by Michael Cohen, Simson Garfinkel and Bradley Schatz. That version can be downloaded from Google Code.

AFFLIBv3 has been depreciated and should not be used for new projects.

Sleuthkit, Autopsy , OSFMount, Xmount, FTK Imager and FTK support the AFFv3 image format.

AFF Background

AFF was created to be an open and extensible file format to store disk images and associated metadata. The goal was to create a disk imaging format that would not lock users into a proprietary format that may limit how he or she may analyze it. An open standard enables investigators to quickly and efficiently use their preferred tools to solve crimes, gather intelligence, and resolve security incidents. The format was implemented in AFFLIB which was distributed with an open source license.

After AFFLIB was published, Joachim Metz published libewf, an open source implementation of the EnCase Expert Witness format. Later, Guidance Software modified its format to allow single disk volumes larger than 4GiB. Together these two changes significantly decreased the need for AFF and AFFLIB.

In 2009 Cohen, Garfinkel and Schatz published an article on AFF4, a new file format that incorporated and expanded on the underlying AFF ideas. AFF4 provides for multiple data views within a single data archives and allows links between archives. As a result, AFF4 natively supports selective imaging, logical file volumes, hash-based imaging, and a variety of case-management scenarios.

AFFv3 Extensions

The original AFF format is a single file that contains segments with drive data and metadata. Its contents can be compressed, but it can be quite large as the data on modern hard disks often reach 100GB in size. AFFv3 supported three file extensions --– AFF, AFD and AFM –-- and provided a tool to easily convert between the variations.

For ease of transfer, large AFF files can be broken into multiple AFD format files. The smaller AFD files can be readily moved around a FAT32 file system which limits files to 2GB or stored on DVDs, which have similar size restrictions. The AFM format stores the metadata in an AFF file, and the disk data in a separate raw file. This format allows analysis tools that support the raw format to access the data, but without losing the metadata.

Compression and Encryption

AFF supports two compression algorithms: zlib, which is fast and reasonably efficient, and LZMA, which is slower but dramatically more efficient. zlib is the same compression algorithm used by EnCase. As a result, AFF files compressed with zlib are roughly the same size as the equivalent EnCase file. AFF files can be recompressed using the LZMA algorithm. These files are anywhere from 1/2 to 1/10th the size of the original AFF/EnCase file.

AFF2.0 supports encryption of disk images. Unlike the password implemented by EnCase, encrypted images cannot be accessed without the necessary encryption key. FTK Imager/FTK added support for this encryption in version 3.0 and are able to create and access AFF encrypted images.

AFFLIBv3 Tools

See Also

External Links