Snort mailing list archives

RE: inside or outside


From: "McCammon, Keith" <Keith.McCammon () eadvancemed com>
Date: Fri, 19 Jul 2002 09:02:18 -0400

http://www.snort.org/docs/faq.html#2.3

If you run Snort on the external interface, pcap will see the traffic regardless.  And if you only have one sensor at 
your disposal, the general recommendation is to place it outside of your firewall.

If you really want a full picture of the traffic that's moving through your network, however, you'll want one sensor in 
and one sensor out.

What I'm trying to spit out is that it's up to you.

-----Original Message-----
From: Seth L. Thomas [mailto:s.thomas4 () comcast net]
Sent: Friday, July 19, 2002 6:48 AM
To: snort-users () lists sourceforge net
Subject: [Snort-users] inside or outside


Sorry if this was covered before but..

Where should snort go, inside or outside of a firewall? Lets 
say you have a
standalone box so when you run snort against the interface to 
the net like
snort -dv -i eth0 then you're actually running snort on the 
outside of the
firewall because it binds to the raw socket so it gets the 
traffic before
your kernel (ipchains/iptables) has time to react to it. 

But if the traffic your sniffing is being blocked by 
ipchains/iptables then
snort wont give you much info because the blocked traffic 
wont be able to
establish a connection so at most you'll capture a SYN. 

But if you run snort against traffic that you allow through 
the firewall
then i mean, it's too late cause you're already letting it 
in. I always
wanted to know a little bit more info about the traffic I'm 
blocking (more
info than what ipchains/iptables gives you) but how can one 
do that without
allowing it in?

 


-- 
Join the Navy; sail to far-off exotic lands, meet 
exciting interesting people, and kill them.


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