Firewall, yay! Protection!...?

Figured I oughta get a firewall up and running on my computer since I'm on the web so much. Duh! Anyways, found a great little tutorial with all kinds of other info on it as well...check it out here. Just note that he instructs you to use the term "aptitude" to get stuff via ubuntu's terminal, from what I understand you're supposed to use "apt-get", but I did just copy a bunch of his commands (including the 'aptitude' command) to install the Java update (JRE v6.0) for firefox, and it went through fine.