Snort mailing list archives

RE: Increase performance with filter or pass-rules


From: SRH-Lists <giermo () 333tech com>
Date: Fri, 21 Nov 2003 09:34:37 -0600

I have a sensor that monitors a network where there's lots of 
VPN-traffic (esp).

Esp is an encrypted protocol, so there's no point that snort looks for
plaintext data within these packets.

Can snort make a pass-rule for the esp protocol, or does it 
only support
ip, udp, tcp and icmp?


Related question:
Is it a bad thing to use a bpf filter to exclude esp?
Is it bad to filter out all tcp/22 and tcp/443 and other encrypted
protocols?

/Martin

Short Answer:  Use a bpf.

Longer answer:  Just because the data in a protocol is encrypted doesn't
mean that snort can't detect "bad things".
Witness the several SSH exploits that snort can detect.

-steve


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