For some reason all the computers in labs on our Novell network would reboot when they received a net msg. As soon as the sysadmin saw that, he deleted all copies for the 'send' executable from the network to prevent this from happening. We wrote a program to mimic the 'send' command, but that was a little boring after the first few times, so we moved on to phase 2.

The network servers were configured to send out a message to everyone connected to it when one of its public shares was nearing capacity. We wrote a program to fill up one of the smaller network drives, causing the server to msg everyone logged in to that server, causing all the computers in all the labs across the school to reboot. The powers that were were not amused, but we were.