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Network Security Snort-Signatures
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Re: [Snort-sigs] Storm worm rule

Subject: Re: [Snort-sigs] Storm worm rule
Date: Wed, 13 Feb 2008 18:06:26 -0600
--On Wednesday, February 13, 2008 16:17:35 -0600 David Thomason 
<dthomason@securityevangelist.com> wrote:

This rule would not trigger on the packet you provided for at least two
reasons.  1.  The content doesn't match.  2) the dsize is > 25.

In your description you said "Normal data payload size is either 2 bytes or
25 bytes".  Since the offset is 46 (start counting at zero) your payload has
to be longer than 25 bytes.
Are you implying that the data payload is different than the setup payload?
If so, you need to use at least two rules.  The first would set a flag if |10
A6| is in the appropriate position and the second rule would check the flag
and then the dsize.


I was wrong about the offset.  The |10 a6| bytes are the first two of the 
payload.

-- 
Paul Schmehl (pauls@utdallas.edu)
Senior Information Security Analyst
The University of Texas at Dallas
http://www.utdallas.edu/ir/security/


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