Snort mailing list archives

Re: Snort rule for a pattern match?


From: Jamie Riden <jamie.riden () gmail com>
Date: Tue, 26 Mar 2013 18:37:02 +0000

I hate to suggest such a kludge, but I'm going to anyway:

Can you just generate all the possible rules using a perl script? Do
we know what range of starting characters are possible?

Joel will be along in a minute to tell you the proper way to do it :)

On 26 March 2013 18:01, Shields, Joseph (NIH/NIEHS) [C]
<joseph.shields () nih gov> wrote:
I’m reposting this question as I have not seen any responses yet.  Perhaps
this can’t be done at this time.



Brian



I am looking for a pattern that identifies a threat I am tracking and need
to write a signature to find it.  The problem is that I don’t know what the
starting character will be but I will always know what the difference
between two given characters will be.



A simple, human readable, example is:



ABCDTSRQ



The difference between each character is:



[A] is 1 SMALLER than [B] is 1 SMALLER than [C] is 1 SMALLER than [D] is 16
SMALLER than [T] is 1 BIGGER than [S] is 1 BIGGER than [R] is 1 BIGGER than
[Q]



The pattern in this example is -1,-1,-1,-16,+1,+1,+1.



BCDEXWVU would match this pattern and so would HIJKZXYW.



How can I write this rule?



Brian




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-- 
Jamie Riden / jamie () honeynet org / jamie.riden () gmail com
http://uk.linkedin.com/in/jamieriden

------------------------------------------------------------------------------
Own the Future-Intel&reg; Level Up Game Demo Contest 2013
Rise to greatness in Intel's independent game demo contest.
Compete for recognition, cash, and the chance to get your game 
on Steam. $5K grand prize plus 10 genre and skill prizes. 
Submit your demo by 6/6/13. http://p.sf.net/sfu/intel_levelupd2d
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Please visit http://blog.snort.org for the latest news about Snort!


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