Snort mailing list archives

Re: heavily switched networks


From: Stewart Larsen <slarsen42 () cfl rr com>
Date: Wed, 24 Dec 2003 10:25:51 -0500

Well, you tell me.  As a network admin in charge of security, should I
be worried about intra-network traffic? 

Would I be better off running a host-based IDS like tripwire on the
servers I care about and only sniffing the uplink?

This is all theoretical, BTW.  But I'm researching for future
opportunities.

Stewart

On Wed, 2003-12-24 at 10:21, Erek Adams wrote:
On Wed, 24 Dec 2003, Stewart Larsen wrote:

right, but where would you tap.

Let's assume that I have the gateway and firewall set up going into a 16
port switch. We'll call this switch switch:0. Each port on switch:0 goes
to another 16 port switch.  We'll call these switch:1 through switch:16.

I now have a nicely divided network with 16 segments of 16 computers
each. That allows me to have 256 computers on my network.

How do I effectively monitor traffic within each segment without a
switch that supports SPAN?  Do I need to sniff on 256 different wires?
or am I missing some fundamental insight here?

Perhaps....

Do you care about network <-> network traffic?  If not, then just sniff
your uplink.  Sniff the pipe from the FW to switch:0 and you catch all the
traffic coming into your network, no matter how many segments you have.

Cheers!

-----
Erek Adams

   "When things get weird, the weird turn pro."   H.S. Thompson
-- 
Stewart Larsen



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