http://www.theregister.co.uk/2009/01/22/mac_trojan_attack/

A trojan delivered using an IWorks 09 download package from warez and torrent sites, is secretly targeting an undisclosed number of websites. make sure you are not one of the reported 20,000 people who have so far been affected.

Make sure that you are aware of every program that is running on your mac. If not bring it along to our next meeting and we can solve the mystery and clean you mac for you.