Learn about iptables

[Jeff]

Here are a couple of excellent resources to help you understand what iptables are and how to manage them.

http://www.sns.ias.edu/~jns/security/iptables/iptables_conntrack.html
http://iptables-tutorial.frozentux.net/iptables-tutorial.html
http://www.justlinux.com/nhf/Security/IPtables_Basics.html