[Snort-users] tcp rules not working

James Lay jlay at ...13475...
Wed Feb 15 22:01:56 EST 2017


Your TCP flow will have a state.  Try flow:established.
James
On Wed, 2017-02-15 at 22:23 +0000, Michael J. Sheldon wrote:
> I'm testing snort for use filtering DNS traffic. I have it set up
> using nfq inline
> 
> This rule works exactly as expected (drops requests for www.example.c
> om):
> drop udp any any -> $HOME_NET $DNS_PORTS (msg:"TEST example.com";
> flow:stateless; content:"|03|www|07|example|03|com|00|"; nocase;
> offset:12; sid:3100001; rev:1;)
> 
> This rule also works (alerts for all tcp inbound):
> alert tcp any any -> $HOME_NET $DNS_PORTS (msg:"TEST all tcp";
> sid:3100003; rev:1;)
> 
> This rule does NOT work:
> drop tcp any any -> $HOME_NET $DNS_PORTS (msg:"TEST example.com";
> flow:stateless; content:"|07|example|03|com|00|"; nocase; offset:12;
> sid:3100002; rev:1;)
> 
> After a LOT of playing with the rules, no matter what, if the
> protocol is TCP, and there is a "content" parameter at all, the rule
> will not match. tried variations on flow (stateless, to_server,
> to_client, etc)
> 
> I've got to be missing something incredibly simple, but at this
> point, no idea what it is.
> 
> Michael Sheldon
> Dev-DNS Services
> GoDaddy.com
> 
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