[Snort-users] How to ignore Referrer: header?

Brian bmc at ...950...
Tue Nov 6 04:17:02 EST 2001


According to Williams Jon:
> I'm getting a lot of false positives on the WEB-MISC http directory
> traversal rule.  In each one, the "../.." part isn't in the actual request,
> its in the Referrer: header.  Is it possible to write the rule in such a
> manner that it only triggers on stuff in the request and ignores the rest of
> the packet?  The rule in question is:
> 
> alert tcp $INTERNAL any -> any 80 (msg:"WEB-MISC http directory traversal";
> flags: A+; content: "../"; reference:arachnids,297;
> classtype:attempted-recon; sid:1113; rev:1;)


Well, if by request you mean URL... Yes.  It is possible.  But not
desired.  If you ignore the rest of the packet, you will ignore POST
data which may include "../../" 

Many CGI applications don't care if you are using GET or POST to send
of variables, and that would be a very simple way to evade your
signatures.

-- 
Why do we have to hide from the police, Daddy?
Because we use vi, son. They use emacs.




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