Wednesday, August 25, 2010


Just heard someone discussing on this 'Fork Bomb'. Folks from core SA background who spend much of their time hardening their server, making it fit and strong enough to withstand the live raw traffic as well as (D)DoS proof might already know it why prank like this exists. For me when I discuss topics like Fork Bomb I rightly say - "It's NOT there, it's needed - that's why it exists!" Even though I don't know if it was a intentional or accidental discovery -computer pranks and some viruses like this(wabbit) I would say, helps us making us aware of our current strengths and weaknesses - but definitely with right spirit and following all safety measures. Fork-bomb can be lethal sometimes and may loose unsafe data too. But at the same time on a newly build server can be one of the point in checklist for kernel 'ulimit' parameter.

Just to touch upon the subject line a bit, A Fork bomb is considered to be the (deadliest) smallest writable virus code in the batch language and it is capable of being annoying and if launched on a computer or server will probably result in a crash.

This is how this forkBomb piece of code looks like:

:(){:|: &};:

- looks like smiley puking? Probably, who wrote this first was a bit humorous cum creative guys who wanted to make it look funny and then attack . Funny earthlings!!!! But don't you dare to underestimate it, even-though it looks like a set of smileys. The below will work fine too, and can prove lethal equally.

nix|nix &

Now to complete this story I must also tell you how to defend against this. For that you need to read and understand all the parameters around this file /etc/security/limits.conf, a bit of PAM, and some ulimit parameters and see you are done!! I am sure doing this, you will also discover so many new dimension on your server hardening mission.

Jai Ho!!

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