We installed Duke Nukem 3D on every computer. It was like one exe file and we’d just drop it into random folders. Then we’d play in typing class and only switch back to typing when the teacher came by.

Friends found a way to get our scheduling website to leak our schedules weeks early completely client-side. Because a lot of schools use that website, the information spread and all of a sudden we had people from Kentucky in our Discord server asking us how to do it. You're welcome, random Kentuckians.

Ok, I'm old and this wasn't a computer prank but it's along the same lines.

I used to have a digital watch that functioned as a small universal remote. (It looked like an 80's calculator watch with tiny numbers.)

You did have to program it with the universal code for that brand, but my middle school had bought their TVs in bulk, so the ones permanently mounted in the rooms were all identical models.

I simply programmed my watch to that model, and I'd occasionally keep turning the TV on during a lesson. I did it fairly infrequently, and always in different classes so as not to give myself away.

I never got caught. Back then Tvs only went to channel 100-120ish without special equipment for satellites. If they went higher I would have LOVED to keep changing it to channel 666.

As a teacher: I would change the computer hooked up to the projector to Dvorak layout and forget to change it back.

Put some VB script (I think) that opened and closed the CD-ROM 50 times inside a startup folder. Did it on all computers. Also put a batch file there that shuts down the computer one second after logging in on all teacher computers.

And last but not least, I created a phishing Facebook page, opened it on some browsers in school, rewrote the URL to a Facebook one (without pressing enter) and left it there, collected some passwords.

Edit: Also installed Ubuntu (dual booted) on the computer I usually used.

Edit2: Disabled the tracking software for a computer I used. Damn, it's all coming back to me! Good times.

We put hamster dance on all the computer lab computers and cranked up the volume to max then locked the door from the inside using a trick, so that they would need to get the facilities people to get in. It was really dumb.

Highschool had filters to prevent students from visiting certain (most) sites, but for some reason a browser created using Visual Basic Studio's browser template worked just fine. At least I think that's what it was called. It's been a minute.

Made a basic script with a nested loop to burn ~20 mins before playing some annoying sounds using the PC speaker. The PC must have been a <=286. I started the script once just before the English teacher arrived and disconnected and hid the keyboard. It resulted in some entertainment when he had to try to silence the PC, but eventually he found the power button.

Installed VNC software on the classroom computer. Simply added a random character when teachers tried to login to various websites, or closed the current page when they weren't looking.

Got caught after a week, for laughing too obviously on the back row.

Nearly got expelled for "hacking", and all staff was recommended to change their passwords for everything.

Figured out how to install a ton of games on school laptops. School was pissed that I was running a Minecraft server

They had both NetSupport and DeepFreeze installed. At the time, NetSupport config files could be decrypted with a simply python script, and contained the password. Turns out, it was the general admin password.

So I had admin creds, full control of any PC with NetSupport, and the ability to install anything on a computer and have it survive past a reboot.

What did I do with it? Video games, mostly.

While not technically a school computer. In college we all had to install a WiFi client to access the school's WiFi. It was shit so I started digging around and found the localization files in plain txt. I then, when I had the opportunity to, booted into a friend's computer with Linux and changed the confirm button to say "I'm a bitch". They never asked me to change it, which I would've, so it just stayed like that all year.

Used netsend to send dank memes to every connected PC in the school.

I realised the school PC’s boot order was A:, then C:, booted into DOS from floppy to get behind their own autoexec.bat, installed my own which just repeatedly echo’d “Teachers suck”.

They had some shitty network config utility, which was relying on a weird script language (from a company called BFC Computers). Anyway, it synced some assets down to customise a series of crappy programs with licenses and “Property of Bangsbostrand Skole” messaging. I changed to it randomly (about once a month, across their fleet or 50-ish PCs) retrieve a different set of strings and pictures which all said “Teachers suck”.

I was banned from the computer lab for a year. They fixed the autoexec issue within a day (after calling “very expensive consultants, young man!!”) but when I left some their PCs would still occasionally display “Teachers suck” instead of “property of” in various programs.

Used a old password sniffer or something that revealed stored password. Turns out it was the root password for the whole school network LMFAO! Still use the password till this day with added characters 😂😂😂

Notepad could read/write everything so I used it to temporarily disable the dumb software that locked things down to a typing game, a "bible study" game, and Notepad. When they found out I wouldn't admit to anything and they had no idea how I did it. I could literally type faster than the computer could keep up with in the typing game so I could sit back while it caught up to me and still get a perfect score, which really sealed the deal for me that they were wasting my time in "typing class" and it wasn't worthwhile to punish me for whatever it was I did that let me take over any school computer I wanted without apparently changing anything about it that they could figure out.

In high school, my friends and I were getting into Ubuntu. We were smug Linux nerds. We came up with the idea of installing Linux on one of the school computers. The challenges in doing so was, how to do so without the teacher noticing and getting into the locked bios. The teacher problem was solved when we got a little bit of time when the teacher would step out of the room sometimes. We picked a desktop that wasn't being used by anyone at the time in the class. The other problem was getting into the bios to boot the drive. Long story short, we were able to switch a jumper on the motherboard to clear the bios settings and let us boot the drive. With Ubuntu installed, it took all of about a day for the school to take that PC to the IT gulag. I think they were very confused and threw it out. We didn't want them to just throw more desktops out so we stopped our shenanigans there.

I ran a cgiproxy instance with proper ssl certs that totally bypassed and trivialized the school's internet filter. It was password protected with unique passwords per user and I had it set up in such a way I could tell when a password "got out" and I'd cancel it. It got added to the blocklist a couple times, but I was ready because I'd already registered like 20 dynamic dns services to point to the server. It would take them months to add it to the manual blocklist but just a minute to change a link on my forum so people used the next address in line. It was an open secret that I was running it, but I was pretty smart in how I ran it and who I provided access to. I also ran a forum that was popular with the student body and the passwords to the proxy were given out there, but only to people I trusted and could reasonably deduce who they were. Even then they didn't know it was me running the whole thing.

I mean most people probably did, but again I did it in such a way there was never any real paper trail. I never made any money or wanted any clout for it. I just thought it was fun that I got pissed off at the internet filter blocking newgrounds one day and thought "absolutely not", and basically trivialized the filter schoolwide.

Not neccesarily the computers but I used to have a phone with an IR blaster on it and had some fun with the projectors doing that

I didn't, but a classmate shoved a piece of pizza in the CD drive.

I'm old enough that typing 55378008 into my scientific calculator and then turning it upside-down absolutely fits the criteria.

I graduated in 2000. During my 11th year, I had an economics class in the same room as a computer lab. Over the course of a few weeks, I downloaded a voice synthesizer program, Shit Talker, to all the computers and set up scripts to have them all begin "talking shit" about our educationally worthless instructor (he taught because he wanted to coach sports), all sequentially during a class a few weeks in the future.

What I didn't think about is how I was one of maybe four or five computer literate students in my grade, so I was quickly targeted after it went off. I should have just denied having done it but I was a dumb teen; they were bluffing about knowing it was me and I fell for it. I had computer access revoked for the rest of my public school career.

Soooo...a bit later that year, my father brings home a very small, defunct computer from his work. It was this custom job consisting of a tiny motherboard, smaller than a micro ATX, with a couple of daughter boards for all its peripheral connections. He just stole it because he thought it was cool but, being pretty computer illiterate, didn't know what to do with it. I gutted it, installed the innards in a plastic file folder box, and installed Windows 98. I now had a portable computer! I'd carry it to my classes, hook it up to a monitor, and use that instead. I initially caught flak for it but I was restricted from using school computers, not their monitors.

Our network had a program called "deep freeze" on every computer that was basically an automatic system restore point.

A friend worked for IT during the summer and got the password to turn it off. I could make any change I wanted and make it 'permanent'. I didn't do this much. My favorite hobby was opening word docs that students saved on shared drives and replacing the word "the" with profanity.

discovered a workaround that i could get to the C drive, then discovered a program that could change the wallpaper and info text on the computer (the change was local to that specific computer). had a little bit of fun with that a couple of times. i also brought in a USB stick with Linux Mint installed on it and booted to that whenever i had free time (i mostly browsed the safe side of the darkweb [back when it was still interesting] and made keygen music in OpenMPT). fun times those were. also booting to mint led me to fully switch to linux so ye :)

Disabled secure boot

Loaded windows pe

Backed up utilman

Replaced utilman with cmd

Rebooted

Installed a ninite package containing steam

Booted into windows pe again

Restored original utilman

Reenabled secure boot

Turned out I couldn't launch steam because of AppLocker

During computer learning in a computer lab 15 years ago, I figured out that the student passwords were sequential, so I could easily guess other students' passwords. If I logged in to their account while they were logged in, they would get booted and I'd hear the inevitable "Mrs Teacher! It says my session expired!"

I did that 2 or 3 times over the course of a few minutes before I got caught. The vice principal rambled on and on about how I was "disrupting learning" and how I "should be suspended for this" before finally telling me, "my mentor taught me a really important lesson. If your students don't hate you, you aren't doing your job."

What a horrible piece of shit.

Uni astronomy lab redhat machines accepted single user mode arguments in grub. Created a backdoor user with uid 0 and wrote some code to play some bleeps and bloops every night at 2am. Only did this to one machine to add to the mystery

In high school, I noticed that our home directories were school ID # + first few letters of last name. The ID numbers were vaguely in alphabetical order, I forget if by first or last name. While the contents were hidden by permissions, I figured out the school ID # of a classmate who had a near school ID # just from the directory name. That was a bit problematic because teachers would use them to post grades in an pseudo-anonymized fashion, the lunchroom used them for accounts, and who knows what else.

I didn't mess with anything, but I did say something to the my tech teacher. She knew I was a sweet kid with a knack for tech and some extra curiosity. She passed me off to the school system administrator, who happened to be a family friend. We talked it over, he asked me not to share my discovery, and that was that. It's been a good twenty years since then so hopefully they're switched to a way of provisioning home directories that doesn't spew PII everywhere.

If WinNuke rings a bell. You remember the fun :-)

Open a small program. Type in the IP address. Click Nuke. Target PC immediately shuts down. While it's rebooting you grab it's IP address as your own so it can't rejoin the network. Worked great in a building where every machine had a predictable fixed ip. Some good teenage mayhem.

My school had a shared drive where anyone could create files and folders. There was one folder where people would put random things (bash scripts downloaded from the internet, pirated minecraft, etc.). I wrote a python program that would display a picture of a pineapple on your screen (no ability to minimise, or move other windows in front of it). I had python installed to one of those folders that only appears if you select "show protected operating system files". I later wrote a remote-control script that communicated by creating files on the network. I was able to control the mouse and keyboards, open applications, take screenshots, and monitor keypresses (I never got anyone to click on it without me telling them to though). Never got discovered for any of it...

Back in the day keyboard and mouse were connected to the back of the computer with identical (but color coded) PS-2 plugs.

Today one would expect that swapping two mechanically identical plugs would result in no major trouble - think USB - but back then COLOR CODES HAD TO BE OBEYED!

Or computer science teacher came to help when our PC won't boot up, tried reset, tried reset again, fiddled with the BIOS, gave up.

That wasted more than halve the lesson's time just for us to swap plugs back to working while he wasn't watching.

Sometimes things simply don't work when the teacher is around...

I wiped a schools Chromebook to install linux on it. Somehow never got caught even when I had to turn in the computer after graduation.

Nice try, FBI guy. We are not divulging any of our past felonies.

Edit: oh boy, was I wrong...

Hosted a MUD. Three batches of comp sci and related majors busily typed on text- based terminals, apparently programming, but were actually adventuring in Midgaard.

"Net send" message to every windows PC in the school. IT was not happy about that. Guess they should've disabled that exploit. I think it was before windows xp had (SP2?) disabled it by default.