Because its aol software ... truly awful provider

I wouldnt worry about attacks for IM convos ... if someone wants to target your computer they will and malware will be picked up more commonly through web browsing

Why not try virtulisation? You can set up the computer as you want and then have one or two applications such as IM software and browsers using virtualisation which means that even if you went on a site crawling with viruses/malicious scripts it wouldnt affect your system or infect it .. works with p2p and IM as well .. have a read of the concept as it may prove beneficial to you ... there are several different programs that do the job but the one below is a good program which is very easy to use
http://www.trustware.com