In eleventh grade, we had a classroom with around 20 486 PCs connected in a token ring network. When the teacher wasn't watching, we used to sneak in Doom on floppies, exit Windows out to the dos prompt, and do a manual install.
This was great, but it was a major hassle to do this every time we wanted to play, and to delete the files afterwards.
I came up with the idea of marking the folders as hidden from DOS, and for that extra obfuscation, renaming the folder to start with an extended ASCII character. Sure enough, no one else but my friends could figure out a way in. (We all had Midnight Commander on floppies to run around such problems).
This all went well for a few weeks until the class teacher must have found some way in that we didn't know about. I got dragged up in front of the principal and accused of "hacking the system", since apparently the teacher couldn't figure out a way to remove the files.
I barely escaped a suspension, but that was a great lesson for me in what happens when you usurp your authority figures.