Some fun ones: BBS games started adding virtual currency that you could transfer between players. Some even participated in a network of BBS systems, allowing

Some fun ones: BBS games started adding virtual currency that you could transfer between players. Some even participated in a network of BBS systems, allowing the movement of game currency from one BBS to another. These frequently didn't have input validation and you could transfer -1 to another player and they'd receive 4294967296 dollars. Unfortunately we were kids and kids do nasty things. We would completely upend a competitive game by giving all the underdogs huge wealth. Pager numbers all fell in the same exchanges. Every number under 123-456-xxxx would be a pager. I wrote a program to war dial all these and leave the same victim's phone number on all the pagers. We did it to a friend and witnessed an endless stream of frustrated calls to their house for a few hours. Brutal. A school system put their mechanical control systems on a modem. We acquired the software and directory that could access these control systems. Not only did they put all the HVAC systems on it, they also added things like emergency and off-hour lighting. Some of the stuff that was controllable through this remote interface was down right scary: boiler pressure measurements, boiler system valves, etc. We weren't stupid enough to mess with that but would have fun turning off all the lights at night, or turning up the heat before the Saturday morning recreation basketball games in the gym.