Quoting John Mark Walker (johnmark@johnmark.org):
Rick is always highly entertaining.
Rick: what will you say about Unix and Linux viruses?
Pretty much a romp through the history of same, with lessons about system security drawn as we go.
I've done that talk before, for EBLUG, but it's been two years, so my hastily-thrown-together slides need revision -- but, for better or worse: http://linuxmafia.com/presentations/