Zip bomb

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A zip bomb, also known[1] as a Zip of Death, Peta bomb or decompression bomb, is a malicious archive file designed to crash or render useless the program or system reading it. It is often employed to disable antivirus software, in order to create an opening for more traditional viruses.

Rather than hijacking the normal operation of the program, a zip bomb allows the program to work as intended, but the archive is carefully crafted so that unpacking it (e.g. by a virus scanner in order to scan for viruses) requires inordinate amounts of time, disk space or memory.

Details and use[edit]

A zip bomb is usually a small file for ease of transport and to avoid suspicion. However, when the file is unpacked its contents are more than the system can handle.

The technique has been used on dialup bulletin board systems.[2]

Most modern antivirus programs can detect whether a file is a zip bomb and so avoid unpacking it.[3]

Another example of a zip bomb is the file 42.zip which is a zip file consisting of 42 kilobytes of compressed data, containing five layers of nested zip files in sets of 16, each bottom layer archive containing a 4.3 gigabyte (4 294 967 295 bytes; ~ 3.99 GiB) file for a total of 4.5 petabytes (4 503 599 626 321 920 bytes; ~ 3.99 PiB) of uncompressed data.[4] This file is still available for download on various websites across the Internet. In many anti-virus scanners, only a few layers of recursion are performed on archives to help prevent attacks that would cause a buffer overflow, an out of memory condition, or exceed an acceptable amount of program execution time. Zip bombs often (if not always) rely on repetition of identical files to achieve their extreme compression ratios. Dynamic programming methods can be employed to limit traversal of such files, so that only one file is followed recursively at each level - effectively converting their exponential growth to linear.

There are also zip files which when uncompressed yield infinitely large output.[5][6]

See also[edit]

References[edit]

  1. ^ "Zip Bomb". 
  2. ^ "DFS #55". Retrieved 2012-10-05. 
  3. ^ Bieringer, Peter (2004-02-12). "AERAsec - Network Security - Eigene Advisories". Retrieved 2011-02-19. 
  4. ^ "42.zip". 
  5. ^ "Zip Files All The Way Down". 
  6. ^ "ZIP File Quine". 

External links[edit]