Did a sorta similar thing on RiscOS, in BASIC, on our high school computers. It would hide in application directories and put itself in as !Boot (so it'd run wh

Did a sorta similar thing on RiscOS, in BASIC, on our high school computers. It would hide in application directories and put itself in as !Boot (so it'd run when the icon was viewed) and then copy itself into any other application that was run/viewed (I forget which.) Being the smartarse I was, I also unlocked the harddrive of some of the computers (hold some key on boot), put it into an installed application, and then relocked it behind me. This way anyone using that computer was guaranteed to get it on their disk. My fall came when I left a disk with the raw source on it with my name on it in the lab and the teacher found it and figured out what it was. Luckily the teacher was a good sort, I got a talking to from the principal, and banned from the lab for the rest of the school year (but it was September, so only a couple of months.) The next year they started giving me a lot more access to our various school machines so that I could do whatever projects I wanted with them, and once they start to do that you don't want to piss them off and have them take it away, so I behaved :)