If you let it, anything in the computer and anything connected to it can be hijacked. Do you want someone reading your e-mail, accessing your banking information, playing with your webcam, using you as part of a bot army, watching the movie in your dvd player, etc?
Since we are talking about Linux here...standard behavior is to whip and re-install the whole system once or twice a year anyway. Unless Ubuntu got really bloated in the least two or three versions, the install from scratch takes approximately twenty minutes, I can't remember what it is, but apt-get and aptitude include a command to export a list of all installed packages that you can plug back in after re-installing to let it automate re-installing your programs. That step will take awhile, though.
Assuming you haven't already done so, that'll whip it out for sure. You need to think more about security, though. The Windows world tries to do everything for you, but you're basically on your own in the Linux world. It's all standard security concerns, but you might not be used to thinking about the standard.
I'll look into the program. I like computer security and there's really not a lot specifically targeted at Linux, so this should be interesting. Probably should do it from a VM, though.