Here is the link: http://ubuntuforums.org/showthread.php?t=159661

I have commented out the emule and bittorent statements since I do not
use either of them.

Even though iptables is part of the distribution of Ubuntu, the
iptables firewall needs to be initialized with rules.

This guide will instruct beginners how to turn on your iptables
firewall with a rather bullet proof set of rules.

I highly recommend you use your Synaptic Package Manager to install
both nmap and nmapfe, and then test your implementation by scanning
all of the 65535 ports with nmapfe.

If you need to allow other services, there is a link near the top of
the webpage to an Advanced version on how to do that.

The guide is straightforward and easy to understand.