Difference between revisions of "Recovering deleted data"

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When the user requests to delete a file, most modern [[operating system]]s generally do not erase the actual data. For example, when a file in a [[FAT]] [[file system]] is deleted, the Root Directory entry and FATs are updated, but the data residing in the Data Area remains intact.
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When the user requests to delete a file, most modern [[operating system]]s do not erase the actual data. Instead, they merely erase a pointer to the file so that the file does not appear in directory listings. These files can be recovered by simply ''undeleting'' the file — that is, restoring the directory entry.
  
== Recovery Programs ==
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For some file systems, such as [[FAT]], the deleted directory entry itself is easily recovered. In these cases the files can be recovered using an ''undelete'' program.  In other cases, however, the directory entry is not available — perhaps because it was overwritten. In these cases the only way that the file can be recovered is through the use of [[Carving|File Carving]].
  
There are many programs that can recover these deleted files. Some of these software packages are specifically designed for forensics purposes. For example, [[Scalpel]] and its predecessor, [[foremost]], were developed to facilitate forensics investigations.
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Using an undelete function on FAT32 can be very dangerous if any files are fragmented. Deleting the file also removes the FAT entry and so the locations of split fragments can no longer be assumed. Forensically, making any changes to a disk is 'not allowed'.
  
== Recovery challenges and test images ==
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=See Also=
 
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[[Carving]]
[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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Latest revision as of 15:34, 24 August 2015

When the user requests to delete a file, most modern operating systems do not erase the actual data. Instead, they merely erase a pointer to the file so that the file does not appear in directory listings. These files can be recovered by simply undeleting the file — that is, restoring the directory entry.

For some file systems, such as FAT, the deleted directory entry itself is easily recovered. In these cases the files can be recovered using an undelete program. In other cases, however, the directory entry is not available — perhaps because it was overwritten. In these cases the only way that the file can be recovered is through the use of File Carving.

Using an undelete function on FAT32 can be very dangerous if any files are fragmented. Deleting the file also removes the FAT entry and so the locations of split fragments can no longer be assumed. Forensically, making any changes to a disk is 'not allowed'.

See Also

Carving