Soln 1: CONVERT to trillian!!!
It rocks.
Soln 2: Change your message accept settings? Such as not letting anyone AIM you that's not on your buddylist.
Soln 3: Check your computer. You may just have installed the said virus with your AIM or gotten it through ads that AIM brings about. Don't be so fast to blame it on the program guys, if you don't ahve a highquality ad sense program running, it may just be your fault for bringing it to your computer.