Snort mailing list archives

Re: RE: rules vs. suppress


From: "Salil D." <salildumbre () rediffmail com>
Date: 24 Mar 2005 06:05:23 -0000

  
Hi there,

I had been sniffing into your mails
a coincidence, I am stuck at snort.conf and writing of rules
I wrote a few of them for TCP and ICMP
the signature table gets updated 
Kindly, please let me know about snort.conf and rules
and also about multiple sensors

Salil.



On Thu, 24 Mar 2005 Lee Clemens wrote :
That all makes sense, but a serious caveat...what suppress statement
wouldn't cause the rule to be pointless? (alert any any <> 10/8 any)

If the rule says alert when the ip is 10.* and I write a suppress for
by_src $HOME_NET and again
by_dst $HOME_NET,

Then any illicit traffic will be suppressed if it is sent to one of my
computers or from one of my computers to one of these non-existent
(shouldn't be) addresses (exactly what I don't want, and the reason for the
rules in the first place).

Am I overlooking a simple solution for this?


-----Original Message-----
From: snort-users-admin () lists sourceforge net
[mailto:snort-users-admin () lists sourceforge net] On Behalf Of Jeremy Hewlett
Sent: Wednesday, March 23, 2005 4:52 PM
To: snort-users () lists sourceforge net
Subject: Re: [Snort-users] rules vs. suppress

On Mon, Mar 21, Lee Clemens wrote:

But my question is this: Would it have been better to simply write
SUPPRESS
rules and specify my network in track by_src and track by_dst, or to keep
these many rules that include every private network except my own.

By adding these 21 rules, you're increasing the inspection time. Each
packet that comes in will be evaluated sequentially against these
rules. Suppression is a better choice, it's a simpler execution path,
and you're not adding any additional rules.




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