I have two of such stories (and may I just add that some of the stories in this thread just blow my mind!):
Shortly before starting my previous job, this happened there: For a while they'd noticed that there seemed to be much more traffic on their servers than usual. This is good, right? We want people using our website!
So they bought more equipment (obviously expensive). After a while, someone began to think that the volume of traffic was unrealistic for what the organization did, so she began to look into it. And found that one of the IT-guys was using the servers for an illegal download service (like a torrent), pirating movies, games, etc. They turned him in, the police showed up, he was arrested, fired, and send a bill from some of the copyright holders of the pirated materials for the equivalent of hundreds of thousands of dollars.
A friend of my family was the manager of a department in a huge, multinational corporation. One day he saw the newest phone bill for his department and noticed that it was somewhat higher than usual - the equivalent of maybe a couple of hundred dollars, but hey, that's how it is every now and then, right? After all, even though his department don't use the phones that much, they do place calls abroad, and maybe this was just a period with some extra phone calls, or some phone calls further away than usual.
Three months later the new phone bill arrives, and it's even higher, so he decides to look into it and gets the list of calls. It turns out someone has been calling phone s*x lines after normal working hours! Luckily, it's pretty clear who it is (since he's the one who's recently begun staying late
), and my acquintance (MA) calls him into his office and has a chat with him. Now, MA is a strict guy, but nice and fair, and he gives the guy the chance to explain himself. He does, he apologizes, and he offers to pay back the money or work some extra unpaid hours.
As I said, MA is a nice guy, and he feels bad for the man in question, due to some personal circumstances, so he tells him not to worry about that, but that obviously it needs to stop.
And of course you all know that it didn't. Next phone bill arrives, and it is even higher. MA gets the list of calls, and his employee has managed to spend more than 11.000 DKR (something like 2,000 USD) on phone s*x *after* their little talk.
He is fired, and the corporation sent him a bill...