He may not be doing anything.. Could be in my situation I was in.. My wife and I used the same computer.. I started noticing that every time I would get off the computer, weather it was going to the bathroom and done for the evening, she would jump on right away.. I would walk into the room and she would click out of something..
She then would use like quotes I have said to people directed to me in a mean manner.. I installed a spying program and seen the evertime I left or got off the computer she was opening the IM history, the internet history etc...
I got her good thogh.. I created a webpage. all that was on it was wrighting asking her by name why she didn't trust me on the computer and why she's checking up on me.. I also coded it to email me and let her know that so she wouldn't be able to deny it..
I then put a tag in the site to create a history and had it named like a porn site..
Sure enough she went there. We then had a long talk about her jelosy and the computer.. I wasn't doing anything wrong. She was just creating bad thoughts in her own head..