[Snort-users] A simple question........

Dennis George easyeinfo at ...131...
Mon Sep 13 20:52:15 EDT 2004


Hi 
 
This is an extract from snort's FAQ (www.snort.org)
==========================================================
    alert tcp any any -> $HOME 80 (content: "foo"; msg: "foo";)
    alert tcp any any -> $HOME 1:1024 (flags: S; msg: "example";)
    alert tcp any any -> $HOME 80 (flags: S; msg: "Port 80 SYN!";)
    alert tcp any any -> $HOME 80 (content: "baz"; msg: "baz";)
 
Note that all three of the port 80 rules will be checked before the "1:1024"
rule due to the order in which the applicable RTN has been created. This is
because the rules parser builds the first chain header for port 80 traffic and
sticks it on the rules list, then on the next rule it sees that a new chain
header is required, so it gets built and put in place. In this case you would
intuitively expect to get the "example" message and never see the "Port 80 SYN!
", but the opposite is true.
==========================================================

So this means that snort will not check further  if any of the rule is matched..... Am I correct ????
 
By the I am using snort 2.1.0 ..... And Is it possible in Snort 2.2.0 ..... Is it the default action in Snort 2.2.0 or do we have to do some work to enable it ????

Pedro Fortuna <pedro.fortuna at ...11827...> wrote:

Hello,

1) In these cases, only the highest priority rule will generate an alert.
2) I dont know the answer for sure, but my guess is:
- if the two rules are equal except for the SID, you'll get two alerts
- if the two rules are completly equal (SID included), you'll get
an error on snort start.

-Pedro Fortuna


Esler, Joel - Contractor" <joel.esler at ...9426...> wrote: 
Depends on what version of Snort you are running.  Apparently Snort 2.2.0 alerts off of multiple rules.
 
Joel


----- Original Message -----
From: Dennis George 
Date: Mon, 13 Sep 2004 02:44:08 -0700 (PDT)
Subject: [Snort-users] A simple question........
To: snort-users at lists.sourceforge.net


Hi all,

I think it will be simple question............ But I am slighlty
confused..........

1) If in my rule file I have 3 rules and in a packet all the 3 rules
get satisfied... do I get all the three alerts ??

2) If I have two identical rules then does snort discard one of the
rule or generate two alerts when that rule is satisfied ???

thanks in advance

Dennis


		
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