Instant messengers and virus question...
A little background first. I built a system for a close friend a while back and at first everything was fine. About 6 months ago, he got a warning from NAV that he was infected with an IRC trojan. NAV was unable to remove the infection so I recommended we do a clean install just to be sure. I went so far as to do a low level format on the hard disk, repartition, format and clean Win2K install. I installed all his apps myself, from known clean source disks. I set him up with NAV again as well as Zonealarm. (is on cablemodem) All was well for about a month, then he got reinfected with the same virus. He claims not to have downloaded any new software or files except for a few MP3s which I scanned and were clean. I scanned all his cd-roms and floppies, nothing. I know for a fact all my media are clean. We rereinstalled everything again and he was reinfected within a week. The only x factor in my eyes is his yahoo messenger. He uses it quite a bit, has probably 30 contacts some of whom he barely knows if at all. He also gets into yahoo chat rooms quite a bit. I am wondering if he is getting infected through his yahoo messenger from one of his contacts? I am not familiar enough with IMs to know how likely this is. I need to figure this out ASAP. Any input is appreciated.
