To what end? Someone is going to have to take a pin to your fantasy of being some kind of hero detective that thwarted the evil criminal with a clever trap, because it just doesn't work that way in the real world.
If someone has penetrated your network security, you should beef up your network security to keep them out. Any evidence you may collect would almost certainly be inadmissible in court if you wanted to sue the person, and even if you turned it over to a law enforcement agency that had the ability, means, and desire to take on your case, they wouldn't be able to use it almost guaranteed.
Figure out the means by which your network was penetrated, or if you're just being paranoid, and then improve said security as needed. A large number of people seem to mistake malware for some kind of "hacker" activity and the like, so first make sure that what you have is an actual network intrusion and not something you're mistaking for an intrusion.
I have someone that has penetrated my network and I want to place a program on my network that will alert me when they have accessed files the system.
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