Linux Networking, Part 6: Securing Your Network - page 4
Preparing for the Worst
The SATAN program is one way to check out your router configuration, but requires another Linux PC running SATAN.
A useful site for network tools, albeit Windows-based, is Gibson Research Corp. Check out the Shields Up! section. It provides a basic test of your Linux router including what services can be seen from the Internet.
Getting access to the Internet is only half the job. Keeping the firewall secure is the other half.