Fork Bomb - ArchWiki

# Fork Bomb

This article or section is a candidate for merging with Security.

Notes: This article is not specific to Arch Linux, it doesn't make much sense here like this; the definition and examples of a fork bomb are all over the internet, and the #Prevention section would make more sense in Security. (Discuss)

A fork bomb is a simple, malicious script designed to consume as much of a system's resources as possible in a very short time frame. It is common for trolls and malicious forum users to try to trick new users into executing fork bombs, which will usually crash an improperly configured computer.

## Scripts

The most common form of a bash fork bomb looks like this:

    $ :(){ :|: & };:

This script will define a function which calls an instance of itself, and then pipes the output of that instance into another instance of itself, then disowns the child processes so the bomb cannot be stopped by killing the parent, then calls the function.

## Prevention

On systems with many, or untrusted users, it is important to limit the number of processes each can run at once, therefore preventing fork bombs and other denial of service attacks. /etc/security/limits.conf determines how many processes each user, or group can have open, and is empty (except for useful comments) by default. adding the following lines to this file will limit all users to 100 active processes, unless they use the ulimit command to explicitly raise their maximum to 200 for one session. These values can be changed according to the appropriate number of processes a user should have running, or the hardware of the box you are administrating.

    * soft nproc 100
    * hard nproc 200

Category:

- Scripts