Difference between pages "File Systems" and "File Carving"

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= Conventional File Systems =
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'''Carving''' is the practice of searching an input for files or other kinds of objects based on content, rather than on metadata. File carving is a powerful tool for recovering files and fragments of files when directory entries are corrupt or missing, as may be the case with old files that have been deleted or when performing an analysis on damaged media. Memory carving is a useful tool for analyzing physical and virtual memory dumps when the memory structures are unknown or have been overwritten.
  
; ffs
 
: The Fast File System, a variant of ufs that is faster and supports symbolic links.
 
  
; ext2fs, ext3
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=File Carving=
: ext2fs was introduced with Linux. ext3 is a journaled version of ext2 which allows for speedy disk recovery after a crash.
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; FAT
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Most file carvers operate by looking for file headers and/or footers, and then "carving out" the blocks between these two boundaries. [[Semantic Carving]] performs carving based on an analysis of the contents of the proposed files.
: Originally used by MSDOS. Includes FAT12 (for floppy disks), FAT16 and FAT32
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; NTFS
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File carving should be done on a [[disk image]], rather than on the original disk.
: The New Technology File System, introduced by Microsoft with Windows NT 4.0. Now used on XP.
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; ufs
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File carving tools are listed on the [[Tools:Data_Recovery]] wiki page.
: The Unix File System, introduced with Unix.
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;
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Many carving programs have an option to only look at or near sector boundaries where headers are found. However, searching the entire input can find files that have been embedded into other files, such as [[JPEG]]s being embedded into [[Microsoft]] [[DOC|Word documents]]. This may be considered an advantage or a disadvantage, depending on the circumstances.
  
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Today most file carving programs will only recover files that are contiguous on the media.
  
= Cryptographic File Systems =
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== FIle Carving Taxonomy==
Cryptographic file systems encrypt information before it is stored on the media. Some of these file systems store encrypted files directly. Others are better thought of as device drivers, which are then used to store some of the file systems discussed above.
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[[Simson Garfinkel]] and [[Joachim Metz]] have proposed the following file carving taxonomy:
  
; Apple's File Vault
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;Header/Maximum (file) size Carving
: A clever user interface to Apple's encrypted disk images. Uses the ".sparseimage" extension on disk files.
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:A method for carving files out of raw data using a distinct header (start of file marker) and a maximum (file) size. This approach works because many file formats (e.g. JPEG, MP3) do not care if additional junk is appended to the end of a valid file.
  
; CFS - Matt Blaze's Cryptographic File System for Unix
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== File Carving challenges and test images ==
: [http://http://www.crypto.com/papers/cfskey.pdf|Key Management in an Encrypting File System], Matt Blaze, USENIX Summer 1994 Technical Conference, Boston, MA, June 1994.
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: [http://http://www.crypto.com/papers/cfs.pdf|A Cryptographic File System for Unix], Matt Blaze, Proceedings of the First ACM Conference on Computer and Communications Security, Fairfax, VA, November 1993.
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; http://www.tcfs.it/
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[http://www.dfrws.org/2006/challenge/]
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File Carving Challenge - [[DFRWS]] 2006
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[http://dftt.sourceforge.net/test6/index.html]
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FAT Undelete Test #1 - Digital Forensics Tool Testing Image (dftt #6)
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[http://dftt.sourceforge.net/test7/index.html]
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NTFS Undelete (and leap year) Test #1 - Digital Forensics Tool Testing Image (dftt #7)
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[http://dftt.sourceforge.net/test11/index.html]
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Basic Data Carving Test - fat32 (by Nick Mikus) - Digital Forensics Tool Testing Image (dftt #11)
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[http://dftt.sourceforge.net/test12/index.html]
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Basic Data Carving Test - ext2 (by Nick Mikus) - Digital Forensics Tool Testing Image (dftt #12)
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==File Carving Bibliography==
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Mikus, Nicholas A. "An analysis of disc carving techniques," Master's Thesis, Naval Postgraduate School. March 2005. http://handle.dtic.mil/100.2/ADA432468
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== See also ==
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[[Tools:Data_Recovery#Carving | FIle Carving Tools]]
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=Memory Carving=

Revision as of 15:04, 1 March 2007

Carving is the practice of searching an input for files or other kinds of objects based on content, rather than on metadata. File carving is a powerful tool for recovering files and fragments of files when directory entries are corrupt or missing, as may be the case with old files that have been deleted or when performing an analysis on damaged media. Memory carving is a useful tool for analyzing physical and virtual memory dumps when the memory structures are unknown or have been overwritten.


File Carving

Most file carvers operate by looking for file headers and/or footers, and then "carving out" the blocks between these two boundaries. Semantic Carving performs carving based on an analysis of the contents of the proposed files.

File carving should be done on a disk image, rather than on the original disk.

File carving tools are listed on the Tools:Data_Recovery wiki page.

Many carving programs have an option to only look at or near sector boundaries where headers are found. However, searching the entire input can find files that have been embedded into other files, such as JPEGs being embedded into Microsoft Word documents. This may be considered an advantage or a disadvantage, depending on the circumstances.

Today most file carving programs will only recover files that are contiguous on the media.

FIle Carving Taxonomy

Simson Garfinkel and Joachim Metz have proposed the following file carving taxonomy:

Header/Maximum (file) size Carving
A method for carving files out of raw data using a distinct header (start of file marker) and a maximum (file) size. This approach works because many file formats (e.g. JPEG, MP3) do not care if additional junk is appended to the end of a valid file.

File Carving challenges and test images

[1] File Carving Challenge - DFRWS 2006

[2] FAT Undelete Test #1 - Digital Forensics Tool Testing Image (dftt #6)

[3] NTFS Undelete (and leap year) Test #1 - Digital Forensics Tool Testing Image (dftt #7)

[4] Basic Data Carving Test - fat32 (by Nick Mikus) - Digital Forensics Tool Testing Image (dftt #11)

[5] Basic Data Carving Test - ext2 (by Nick Mikus) - Digital Forensics Tool Testing Image (dftt #12)

File Carving Bibliography

Mikus, Nicholas A. "An analysis of disc carving techniques," Master's Thesis, Naval Postgraduate School. March 2005. http://handle.dtic.mil/100.2/ADA432468

See also

FIle Carving Tools

Memory Carving