I'm not really a newbie, in fact, i think i know quite a bit about computer security, but this one incident just isn't making sense...

Yesterday I was talking to a friend on aim to try to help him get rid of a trojan that was in his computer when all of a sudden a strange screename that I had never seen before started talking to me and saying some of the stuff I was sending to the other person.

I tried the most obvious things, used a spyware scanner, ran antivirus(both which i have multiple programs I use), went into the command prompt and typed "netstat -n" to look for suspicious ports. All of this stuff did nothing.

How is this person able to see what i am typing? Any help would be greatly appreciated.