OMG! MAXIMOP! That takes me back!
Many moons ago (Early 80s), one was a student of Electrickery and Electronics at the local Technical College (Great place - was taught my trade by people who had been there, done that, and actually gave a shit).
Some of us took advantage of the 'Open Access' sessions run by the computing department to learn about the machine we had experienced from High Skool via dial up acoustic coupler and pukka Teletype machines, punched tape and all (Login was S0531HELLSDN if anyone is interested/bothered!). IIRC it was some sort of ICL Mainframe, I forget which model.
Shortly after I arrived for my secondary education it was replaced by a Harris S800 system, involving time-sharing between serial CRT terminals - luxury! The system documentation available was excellent and available to all in ring-binders stored in the 'Terminal Room'.
One of the commands that intrigued us power-hungry PFYs was 'TT', which was short for "Terminate Terminal" i.e. 'kicked'/forced logoff of a numerically-identified terminal. However, very correctly, it wasn't available to us plebs, just the Operator Gods.
I wrote a typical* Startrek game (50x50 Universe, Federation vs Klingons, Phasers, Photon torpedo weapons, bonus squares, traps for the unwary...bit of a cross between a MUD, Startrek and levels of deviousness a really nasty DM would have been proud of). Not bad for the time, and it made it onto the system 'Games pack' (Yep ED Packs had replaced the vacuum column tapes of the ICL system). I wonder if someone still remembers '2256E*TREK'.
After having the source code stolen by a serial-port-swapping arsehole (No consequences in those days), I beefed things up, including a way of dropping the banhammer on the arsehole (Who couldn't understand what he'd nicked) with my *own* version of the 'TT' command, which involved setting things up so that the user was logged out if the program encountered an error...plus a very deliberate div/zero when the 'TT' message arrived at the terminal number in question via an inter-process mailbox.
All was fine, until one evening I spotted terminal ID '0' being used to play it, with a UID of 'OPERATOR' shown. As a small act of rebellion, I thought it would be fun to terminate that session, as the operators were forever bollocking and banning us for playing games during 'Educational Time'...so I hurled a 'TT' event towards terminal 0. Being on fairly good terms with the ops, I was sure they'd see the funny side. And *they* did.
Their boss didn't...as when terminal 0 (The system console) logs off, the entire machine abruptly dropped back to single user mode, necessitating a full 'cold boot'. Ooopps.
Downtime was in the order of 15 mins, but apparently it messed up several important batch jobs from real academics and real-time interactive sessions from remote evening/night classes.
To his credit, after dispensing a big bollocking (in person and by proxy) he had the grace to ask how I managed to do that. On reflection, it could have been fun explaining to Head-Of-Computing and one of his A/Ps how I did it but I was shitting myself the entire time!
*For the time..