Right, I can almost guarantee you that your IT Department doesn't have time or care about what you're doing but it's not them you have to worry about per se, it's the capability. When they start looking it's because management directed them to. Sometimes it's so they can have hard evidence to hold against you, document on your record for future use, or worse. It might be completely unrelated to whatever they are unhappy with you over but somewhere in the new hire paper work or employee handbook you probably signed a computer use type of contract that you didn't read. Another thing, when I've seen this type of action taken, the surveillance can last for weeks and the user has no clue.