Lets say I thought my computer was either hacked or someone was capturing my packets or logging keystrokes or whatever, and I wanted to get some software that could monitor all background activity and/or internet protocols and sent/recieved data. What software would I want?

Rule out virus and trojans and the like. If this is happening, it is way beyond the 15 year old little punk hacker wanna be's. I have a solid reason for my suspicion, and it is irrevalent to the question I am asking in my opinion. The individuals involved would be considered pro's, lets just say that.

Any ideas would be appreciated