Perhaps the First Denial of Service (DoS) Attack?

An anonymous reader writes: Way back in 1974, Dave Dennis, then aged 13, decided to try out the -ext- TUTOR command on the PLATO system at the University of Illinois, and see if he could cause all the terminals of other users to go offline. It worked. And he never got caught. Of course, the powers that be eventually caught on and fixed the -ext- command so terminals by default didn't automatically receive -ext-'s sent from other locations.