firewalling behind NAT?

["Thomas O'Dowd" <tom@example.com>]

Hi,

Quick question, do you need to use a firewall if you are behind a NAT
router? Ie, my machine has a non-routable ip address and the gateway
is a separate box (in this case, an ADSL router) on the LAN. I filter all
open ports on the router to only accept incoming connections to the router
on the internal interface. Quick port scan from the outside confirmed this.
Since I'm not really filtering anything else right now, can a cracker
somehow find away through my router to a NAT'd machine on the inside? I
don't think so, but I could be wrong?

Also, just installed RH7.1 and think it is kinda wierd that they start
with ipchain policies of accept and add explicit things to drop rather
than a policy of drop and the other way round, which is probably the
way that I would do it.

Cheers,

Tom.
-- 
Thomas O'Dowd. - Nooping - http://nooper.com
tom@example.com - Testing - http://nooper.co.jp/labs