On our high-school network, the Guest account had NET SEND privileges. It was somehow less chaotic than one might expect.
We had a single shared T1 pipe for the whole district. Which was enough for email and stuff, but when web browsers got popular, it was suddenly woefully inadequate.
So I figured out I could NET SEND * SERVER ROOM POWER FAILURE - 9 MINUTES OF BATTERY REMAIN - SAVE YOUR WORK AND LOG OUT and after a flurry of traffic, the network fell to nearly-idle. I could max out the T1 with whatever I needed to do for a few minutes, then NET SEND * SERVER ROOM POWER RESTORED and nobody would be the wiser.
The admin did go check on the "flaky UPS" a few times before looking closely at the message. Had a good laugh and told me not to use it too often.
This is along the lines of my early days learning about computers at school. I saw executables were filled with weird junk when looked at in a text viewer. So I'd load a little of that junk in a file and add
CRITICAL DISK ERROR. TURN OFF SYSTEM TO AVOID CATASTROPHIC DATA LOSS
and then printed it out to a system printer students didn't have access too. So you got a page of random symbols and that error.
Little did I know the company adding more computers to the network was there that day and the guy panicked and had the system shut down, it was down the next day too. I never did ask what happened to bring attention to myself, and this was before we had individual accounts in the system.
I remember someone getting a bit wild with their netsend and accidentally spamming the entire school district, including the administration. We also found out that you could DoS your instructor with enough messages.
