Geoff,
Please don't take the fact that you run a Linux operating system as some form of protection. Whilst the various Linux systems are less prone to attacks it does not mean that they are immune. I subscribe to a site which does its best to collate and distribute information regarding weaknesses in operating systems and programs. Gentoo, Debian, Red Hat, and other Linux O/S feature often enough to indicate that they do have faults that are able to be exploited by those inclined to such activities.
*edit*
I don't know just how good the information is but I sure as heck am not complaining. If you are interested then visit:
http://secunia.com/mailing_lists/
and sign up for the advisories - it's first on the list.
If you do then be prepared for lots of e-mails each day (many of which will not apply to you).