Algorithmic Bugs

[Dave Aitel <dave () immunityinc com>]

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Best paper at a conference I went to recently here in Miami Beach.


http://www.cs.wisc.edu/~smithr/pubs/acsac2006.pdf

Summery:
You can send a remarkably small stream of data at a NIDS and cause it
to go to 100% CPU and stop doing analysis if you send the RIGHT stream
of data. This is basically undetectable (i.e. does not crash snort).
Was fixed in Snort 2.6.1 (I believe). Some snort rules have a 1
million to 1 expansion if you do it right (from what I read - I
haven't tested this out yet - but it would make a great CANVAS module!)

The presentation is clearer than the paper. I hope they put it online.

Similar bugs exist in major commercial Python exploitation frameworks
(i.e. you can tartrap CANVAS if you do it right). The more high level
the language, the easier it is to get caught by something like this.

- -dave
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