I just got my cable modem up and running.  My plan is to plug a linux box
into the cable modem as a router and have multiple boxen behind it.  I
also want to run Apache, sendmail, IRC, SSH, and a few other services on
it.  The problem is firewalling.  I like to write TIGHT scripts (after
being comprimised once I'm a little over-paranoid) by opening up just the
service I need and DENYing any other packet from any source that's not on
my specific guest list.

The problem here is that everything inside the router gets blocked.  ICQ,
Napster, and a plethora of other oddball IP apps stop working because I've
firewalled them out, but I don't want people breaking into my router.  Is
there a good way to run this setup?

-Brian