btw, sophos reports, 60% of all malware is in the form of trojans.
the total number of trojans in their list exceeds the number of viruses, worms, etc by a huge margin.
a firewall is always the first line of defense, against internet threats, and can be a great help in stopping trojans !
ewido anti-spyware and a-squared are two of the best freeware anti-trojans.