Snort mailing list archives

Re: [Snort-sigs] P2P GNUTella GET causes lots of false positives


From: "jon baer" <security () jonbaer net>
Date: Thu, 4 Sep 2003 17:12:02 -0400

I had to change it to "GET /uri-res/" (|47 45 54 20 2f 75 72 69 2d 72 65 73
2f|) to monitor correctly ...

- Jon

----- Original Message -----
From: "Shane Smith" <shane () crownbank com>
To: <snort-sigs () lists sourceforge net>
Sent: Thursday, September 04, 2003 3:29 PM
Subject: [Snort-sigs] P2P GNUTella GET causes lots of false positives


Hey Folks,

I'm new to snort, so sorry if this has been covered recently.  SID 1432
regarding p2p networks seems weird to me.

alert tcp $HOME_NET any -> $EXTERNAL_NET !80 (msg:"P2P GNUTella GET";
flow:to_server,established; content:"GET "; offset:0; depth:4;
classtype:policy-violation; sid:1432; rev:4;)

If I am reading this correctly, than any packet containing "GET" headed
out
of my network, destined for any port other than 80 will trigger this rule.

Won't this cause a false positive with every HTTP GET request to any
external server with non-standard ports?

For example:
http://www.nhc.rtp.nc.us:8080/

Simply hitting that URL, causes the rule to fire.

Thanks folks,
Shane



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