I remember in high school poking around a network drive until I found an executable with the name "SEND" in the name. I had a sense that it would send some kind of message somewhere, but I honestly didn't know where or to how many people. I was quite surprised when all the screens in our computer lab froze and, five seconds later, my message appeared on all of them. (I later learned that my message appeared on every desktop screen in the school!)
I'm not sure exactly how they found me out, but I was called into the IT admin's office a couple of days later. She was furious with me. I told her the truth. I didn't know what exactly would happen when I ran that command, but she didn't buy it. Fortunately, nothing ended up happening after that.
I've wondered to this day what exactly they could have done to me if they decided to press whatever legal authority they might have had to its fullest extent. I was never told "don't go to Z:\" or "don't run any program other than those on this list." Even after I was found out, I wasn't ever explicitly told that my actions constituted unauthorized access.
It was a different, perhaps more innocent (or ignorant) time back then. How much have things changed now?
* SEND happened
* Minor kerfluffle ensued among various functionaries
* Big Boss worried that something Big was going on
* IT admin was questioned and had no answers
* Simmer for a few days, Big Boss repeating questions and IT admin being flummoxed
* Eventually adequate logs are found and correlated that place you as the likely responsible party
* IT admin is lathered up about a big nothing because Big Boss keeps asking and their competence is in question
* IT admin unleashes the pent up frustration of a few days of stupidity and job security uncertainty on you, and is not satisfied that all this drama was initiated by boredom and not malice
* IT admin reports to Big Boss, who basically brushes it off because they have moved on to other things -- and at the end of the day knows they run an organization filled with kids, some of whom are more curious than others
* Issue disappears