Re: Rule efficiency

["Isherwood, Jeffrey - IS" <Jeffrey.Isherwood () itt com>]

Yes I did see that snippet of rule... very nice... would that work more efficient than using the "http_header" option 
with my previous content search of: (content:"crappydomain.com";

Or does the one that you proposed:  (content:"|0d 0a|Host\: crappydomain.com|0d 0a|"

Work faster or more accurately?

I asked the bosses this morning BTW if they wanted http traffic to crappydomain.com or all TCP traffic, and they were 
unsure... they will be getting back to me.  I have a sinking suspicion that they want ALL traffic tho, based upon 
"looks" I got when I asked the question.

If they come back with "Yes we want all TCP traffic headed there" I will need to find a way to look only for traffic 
headed there instead of simply traffic that contains the term, as the blog posting that points or mentions 
"crappydomain.com" is setting off my rules with false positives.


Jeffrey Isherwood, CISSP, C|EH
Computer Security Analyst | Enterprise Protection & Planning
Information Systems | Information Protection & Sharing

-----Original Message-----
From: waldo kitty [mailto:wkitty42 () windstream net]
Sent: Saturday, July 24, 2010 2:16 AM
Subject: Re: [Snort-users] Rule efficiency

On 7/23/2010 16:12, Isherwood, Jeffrey - IS wrote:
> > If it turns out that mgmt DOES want just web traffic, the use of the
> > http_header will tell the sensors to stop alerting on the content on
> > pages then correct? I have been getting false positives where a user
> > visits a page with a link or mention of “crappydomain.com” on it and
> > that visit sets off the alert…

> this is exactly the false positive i was speaking of... forum pages with discussions
> about crappydomain.com was one i was thinking... these mailing list posts are another
> very prominent example ;)
>
> did you see my offering where we use content like you are and then include an anchor
> on the http host header without using the http_header option?

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