Re: using a tap

[Michael Boman <michael.boman () boseco com>]

On Fri, 2004-06-11 at 13:41, Altrock, Jens wrote:
> hi there,
> we're thinking about buying a tap too, but there are some questions that I
> need to be answered before:
>
> 1. Taps use to channels to get the traffic to the monitoring device (one for
> RX and one for TX). How do I "bond" these channels 
> together, if I do need to do that?

Please state your operating system. With Linux you do 'ifenslave', and
if you use a RedHat based distribution
http://www.linuxgazette.com/node/view/8937 might be of help.

> 2. It is a security violation when using a Sensor connected to the Tap and
> (!) to the internal net (with IP), but it is needed anyway for updating
> rules and 
> other issues. Is it anyway reliable? 

The tap is a read only connection, and you need a way to:
a) View the alerts
b) Update the signatures

which usually mean one more cable to a special analyst LAN (or your
local LAN, depending how much money you have to spend..). You can have
an semi air-gapped NIDS sensor, where the only connection is the TAP. If
you are in that situation You have to use the plain ol' sneaker net to
transfer signature updates (hint: a USB thumb drive stores bigger files
and are more reliable then the old 3.5" floppies). For system updates:
well, they do 1 GB thumb drives now days..

Also, in those circumstances you (should) have a different PC just
beside it to do the lookups and signature research. Won't be as
effective, but it is doable.. So far I have only seen military
installations of this kind, but what-ever floats your boat...

And when it comes to reliability of the setup: as long as you don't
transfer data from the sensor to the internal network you don't expose
the LAN to any additional dangers..

Best regards
 Michael Boman

-- 
Michael Boman <michael.boman () boseco com>
BOSECO Internet Security Solutions - http://www.boseco.com



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