RE: Bridging as sniffing method?

["Admin.mmm" <admin.mmm () iinet net au>]

Of course if you want to do some individual node testing, you could do worse
than look at ettercap.

I have used it on a number of occasions to reduce what I am looking at.
It filters well at high utilisation.  The only fall back is that it uses ARP
poisoning to grab the traffic, through the switches.

If you want to see all the traffic (as much as the span can hold and not
lose) then perhaps the span port is the best way to go.

Using ettercap, ethereal and span ports together, can make for many options
and filtering.

J

-----Original Message-----
From: Bojan Zdrnja [mailto:bojan.zdrnja () gmail com] 
Sent: Monday, May 08, 2006 2:38 PM
To: Rob Mason
Cc: pen-test () securityfocus com
Subject: Re: Bridging as sniffing method?

Hi Rob,

On 5/8/06, Rob Mason <rob () cissp org uk> wrote:
> Of these, I'm inclined to go with span ports or the network tap as the
> best solution.  However, bridging intrigues me.  Has anyone on the list
> had any experience (good or bad) with establishing a bridge to sniff
> switched LAN traffic?  I've tested out a working config using FreeBSD
> with two NICs and it appears to work OK, but I'm not confident of the
> robustness or integrity of the bridge - any advice would be most
> appreciated...

Span ports will be the easiest solution, provided that you have access
to the switch(es), of course. Keep in mind that if the network traffic
is very high that you will start loosing packets (as you will span all
other ports to this one).

I've been using OpenBSD firewalls in bridging mode for years and there
were absolutely no problems regarding robustness or integrity, and
those firewalls worked on some heavily utilized networks.

Cheers,

Bojan

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