At the moment we are tracking a Trojan that is spreading through Messenger and AIM. It is called Win32/Pushbot.BD and you can find additional information on our Malware Protection Center.
This just give me the opportunity to remind you that you definitely should make sure that files that are downloaded via IM are scanned by your AV-engine. How to do that? Well, it is described here.
Source:? Roger's Security Blog
Trojan, Malware, Messenger, AIM