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Anon sets up a prank at school (sh.itjust.works)

submitted 6 days ago by [email protected] to c/[email protected]

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[–] [email protected] 57 points 6 days ago* (last edited 6 days ago) (3 children)

In university we were taught C programming. We started with simple things like loops and stuff. After a while the topic processes, threads & stuff came up and of course we were instructed to use that.

In the computer lab there where only thin clients so everything actually ran on the server.

A good friend of mine - not know what was about to happen - entered:

while (true) {
    fork();
}

Astoundingly it took a whole minute until the server froze. 🤣
That was the same server most of the school stuff ran on. So nearly everything went down. 😂
He got scolded by the sysadmin the next day but nothing serious happened.

[–] [email protected] 58 points 6 days ago (1 children)

I'd scold the sysadmin instead for not cofiguring critical systems in a secure way. Ulimit exists for a reason.

[–] [email protected] 2 points 5 days ago (1 children)

Huh. I never made that connection before. I always thought ulimit was to prevent excessive disk writes or something

[–] [email protected] 2 points 5 days ago

ulimit -H -u 10 will (hard)limit the current process (the shell) to 10 subprocesses. You can also use it to limit the number of open files etc.

To globally configure that for a user/group you'd use /etc/security/limits.conf instead.

If you want to prevent users from filling up the disk, take a look into quota.

[–] [email protected] 8 points 6 days ago (1 children)

What does that command do?

[–] [email protected] 19 points 6 days ago

Creates a new process. So, it would create an infinite amount of processes filling RAM.

[–] [email protected] 2 points 5 days ago* (last edited 5 days ago)

:(){ :|:& };:

or (more clearly written):

function forkbomb() {
    forkbomb | forkbomb &  ## background the process whilst recursing
    ## the pipe ensures that both instances are called at the same time, instead of waiting on the other
    ## without the pipe, you just get a linear increase in processes. Slow bomb. We want fast.
};
forkbomb  ## start it all off