I was banned from the school computer suites several times for (ab)using net send. Good times.

I remember someone getting a bit wild with their netsend and accidentally spamming the entire school district, including the administration. We also found out that you could DoS your instructor with enough messages.

On our high-school network, the Guest account had NET SEND privileges. It was somehow less chaotic than one might expect.

We had a single shared T1 pipe for the whole district. Which was enough for email and stuff, but when web browsers got popular, it was suddenly woefully inadequate.

So I figured out I could NET SEND * SERVER ROOM POWER FAILURE - 9 MINUTES OF BATTERY REMAIN - SAVE YOUR WORK AND LOG OUT and after a flurry of traffic, the network fell to nearly-idle. I could max out the T1 with whatever I needed to do for a few minutes, then NET SEND * SERVER ROOM POWER RESTORED and nobody would be the wiser.

The admin did go check on the "flaky UPS" a few times before looking closely at the message. Had a good laugh and told me not to use it too often.

A great story and true BSOD material!

BOFH?

Thanks. This was what I was going for but my brain had other ideas.

This is along the lines of my early days learning about computers at school. I saw executables were filled with weird junk when looked at in a text viewer. So I'd load a little of that junk in a file and add

CRITICAL DISK ERROR. TURN OFF SYSTEM TO AVOID CATASTROPHIC DATA LOSS

and then printed it out to a system printer students didn't have access too. So you got a page of random symbols and that error.

Little did I know the company adding more computers to the network was there that day and the guy panicked and had the system shut down, it was down the next day too. I never did ask what happened to bring attention to myself, and this was before we had individual accounts in the system.

the key "feature" of the exploit was the ability to send messages anonymously. the unix commands "write" and "wall" allow you to send a message to any users terminal.

apparently "wall" has a switch "-n" to hide the sender

https://unix.stackexchange.com/questions/99460/sending-messa...

for windows there was "net send" which could be exploited by a tool called NetSendFaker, but this was 1991, so i doubt that already existed.

There was a time on some UNIXes where you could just write to other people's ttys, no write/wall needed, just echo >/dev/...

Making write/wall sgid, and restricting tty write access to that group, was a significant security upgrade back in the day.

I remember in the mid to late 90's when you could get spam from outside of your network via net send. Happy days...

Wall

I was able to use samba to generate these messages such that they looked like they came from other users in the lab. We had a lot of fun with that.