(Il)legal matter
while I can't directly answer that (especially since laws vary depending on which country your in), I know nobody is going to come after you unless you actually do some damage with a serious price tag on it. No police department or security agency could possibly handle the caseload of everyone who managed to break through one of the millions of servers security without doing any damage.
Unless the cops are after you for another reason and just looking for a legitimate charge to bust you on, I wouldn't worry about it. legal or not, there just isn't the man power to go after something so small.
Most likely, the network admin will just sweep the problem under rug if it's noted in the logs. If he's smart, he'll try to fix the problem, and if he's lazy he'll just ignore it. Either way, involving other parties just creates more unneccessary work for himself, as well as puts his competence in question since he let someone slip through security in the first place. It's the same reason that even armored car heists often go unreported. The security corporations would rather take the loss rather then look like they are incompetent.
-Intrus- wrote: so what everyone else is implying is , say if someone came into your house without damaging anything while your not there they get let off the hook , thats not the case in my mind i say its not safe to fuck around unless you use a proxy
A better analogy is if you came home to find evidence that someone was previously in your house but didn't damage or take anything. The most likely response would be to install better locks the next day. But even if you went to file a police report, it's unlikely the cops would seriously investigate the crime and try to track you down.
You are right though that you should use a proxy regardless. Even if it's unlikely to matter, it's just good practice to do so anyway.