The BBC Micro / Econet network used in UK schools was a lot of fun, very open, and not at all secure. There was no internet so you had to work everything out by reading the docs (which were very good) and reverse engineering.
Each account started with a quota (8K!), but you could easily steal more if you could persuade someone to run a program under your control. That was because if they created a file in your directory, and you deleted that file, then the quota to write the file came from their account, but deleting the file credited the quota back to your account. Needless to say I had a lot of spare quota after a while, so much so that I had to "hide" the fact by creating lots of random-filled files, since the system only tracked quota for free space, possibly the root cause of the bug.
Another one was that writing to address 3362 allowed you to change your station number (think IP address if you only had 256 addresses) on the Econet network. So you could trivially impersonate any other logged in account by assuming their station number and sending requests to the file server. I worked out the address (3362) by printing every address that contained the same byte as the station number across a few machines and cross-referencing them by hand.
Another one was the *NOTIFY command which sent messages to other machines on the network. Except it worked by literally typing those strings as if they had been entered on the keyboard of the other machine, obviously allowing you to send arbitrary commands. The system admins at our school removed the program but couldn't remove the underlying "system call" [as we'd refer to it nowadays] in ROM, so I wrote a program that performed a broadcast notify letting you type commands to as many other machines in the room as you liked.
I was banned from the school computer room after a couple of years of this.
One great way to get banned from school computers is to have any talent at computing. It's a bit like banning the kids with music talent from music class.
Quite the opposite here. The IT person, a former mathematics teacher, had no idea about anything so she let us run the old Econet network. They'd send students around with boxes of EPROMs and a screwdriver while she'd sit in her office smoking.
> Each account started with a quota (8K!), but you could easily steal more if you could persuade someone to run a program under your control. That was because if they created a file in your directory, and you deleted that file, then the quota to write the file came from their account, but deleting the file credited the quota back to your account. Needless to say I had a lot of spare quota after a while, so much so that I had to "hide" the fact by creating lots of random-filled files, since the system only tracked quota for free space, possibly the root cause of the bug.
Memory unlocked! We had a messaging program that worked by passing files between accounts. I modded it to siphon a few bytes into my account every time a message was sent, and I added some extra features to make it more attractive than the original version (wish I could remember what I added).
I was banned from the school computer room within a few days of my first computer lesson.
Also using BBC Micro / Econet. While the teacher was typing in their admin password to the Econet file server, I quickly typed a one-liner on one of the BBC Micros in the class that all of us children could see.
It fetched the contents of the keyboard buffer from the file server repeatedly and displayed it on the BBC Micro screen. So we watched, fascinated, as the teacher's very secret admin password appeared one character at a time on our screen.
After logging in, teacher turned round to see what the class was so excited by, and then I was banned from that room for the next 5 years. Never saw it again, couldn't take computer studies as a class.
Even so, when the school held a programming competition to make a pretty demo, I won the competition with my animated story about a plant being rained on and growing to a big happy plant, complete with music and unfurling leaves. Programmed outside school of course.
It was also possible to jam the network by futzing with the MC68B54 registers on any beeb. Can’t remember exactly how though as it was so long ago. Also breaking into the clock boxes and setting the rate too high for the cable span.
Each account started with a quota (8K!), but you could easily steal more if you could persuade someone to run a program under your control. That was because if they created a file in your directory, and you deleted that file, then the quota to write the file came from their account, but deleting the file credited the quota back to your account. Needless to say I had a lot of spare quota after a while, so much so that I had to "hide" the fact by creating lots of random-filled files, since the system only tracked quota for free space, possibly the root cause of the bug.
Another one was that writing to address 3362 allowed you to change your station number (think IP address if you only had 256 addresses) on the Econet network. So you could trivially impersonate any other logged in account by assuming their station number and sending requests to the file server. I worked out the address (3362) by printing every address that contained the same byte as the station number across a few machines and cross-referencing them by hand.
Another one was the *NOTIFY command which sent messages to other machines on the network. Except it worked by literally typing those strings as if they had been entered on the keyboard of the other machine, obviously allowing you to send arbitrary commands. The system admins at our school removed the program but couldn't remove the underlying "system call" [as we'd refer to it nowadays] in ROM, so I wrote a program that performed a broadcast notify letting you type commands to as many other machines in the room as you liked.
I was banned from the school computer room after a couple of years of this.