[Snort-users] Syn-Flood

Matt Kettler mkettler at ...4108...
Wed Nov 12 09:52:06 EST 2003

At 10:47 AM 11/12/2003, Frank Barton wrote:
>I've been looking for a rule that would detect a syn-flood. and the only 
>way I can think of
>doing this would be with N "activate" rules (Where N is the number of SYN 
>packets that
>arive in a specified time), and I think there's got to be a better way.
>after reading the rules for dos-attacks, all I saw was that each tool that 
>is detected, is
>detected by some content string, not specifically by a volume.
>the documentation pdf doesn't have anything in it about a "count" option, 
>or any other way
>that I can think of to count packets.
>if anybody has any ideas, I'd be most thankful.

This would really need to be done in the code itself with some kind of 
variant of spp_portscan. (the classic spp_portscan is implemented as an 
event counter, which is exactly what you'd need)

Code-wise it would be fairly trivial to modify spp_portscan's basic logic 
to be a synflood detector instead of a portscan detector.. but AFAIK 
nobody's done it before.

If you dig in the archives, you'll find this exact topic has been discussed 


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