In high school we found we could use netsend to send messages to other computers; or every computer on the network at once. The rest of the school year was a back and forward where the sysadmins would try to block us and we would find ways around it. I think the final method that worked was writing vbscript macros inside Excel.
I found that trick and showed it to some friends... But it's hard to keep a secret, and somehow a larger non-friend group was using it to cheat in a computer-lab class. I was offended by the blatant cheating, and a little by the idea that certain people I didn't particularly like were profiting from what I'd found.
So I spoofed the system administrator's username (not hard on Win9x) and sent off a stern warning, which must've surprised them since suddenly all the messages stopped. :)
I installed a FTP server on the professors computer. It automatically shared your network disk once you logged in. All the COBOL assignments and solutions where there. Juvenile but hey....
