amiller,
There are a few different ways to test a firewall. I will cover a few
First download nmap and test the firewall with it (from inside and outside if possible). nmap is available from
http://www.insecure.org/nmap/ and is basically a VERY advanced port scanner. There are also a few very good online scanners. Two that I can think of off the top of my head are ShieldsUP and dslreports secureme (
http://www.grc.com and
http://www.secure-me.net respectively).
If you would like a better overall view of the security/integrity of your network I would highly recommend you run both nessus and SAINT (
http://www.nessus.org and
http://www.wwdsi.com/saint) which are IMHO the two best security auditing tools around.
If you need to tweak your rules (I assume you are running ipchains) I would head over to
http://www.linux-firewall-tools.com/...all/index.html which is a great online resource. (BTW I own the book that he is plugging on that page - I definitely recommend it).
Last but certainly not least your could always give us your IP and see what kind of damage we could do
