A fork is a system call in Unix and Linux operating systems that creates a new process, known as a child process, by duplicating an existing process, referred to as the parent process. This functionality allows both the parent and child processes to execute distinct tasks concurrently. The child process is an exact copy of the parent process, except for the unique process ID and a few other attributes. Forking is a fundamental concept in these operating systems and is used for various purposes, including creating new processes for executing different programs and managing multitasking.
A fork bomb, also known as a “rabbit virus,” is a type of denial-of-service (DoS) attack that exploits the fork system call. In this attack, a malicious process repeatedly uses the fork call to create new processes, which in turn create even more processes, leading to a rapid and exponential growth in the number of processes. This recursive process continues until the system runs out of resources, such as memory or process slots, causing it to become overloaded and unresponsive.
The primary goal of a fork bomb is to exhaust the system’s resources, making it unable to perform its intended functions or respond to user inputs. The attack can effectively bring down a system, rendering it unusable until it is restarted or the malicious processes are terminated. Fork bombs are relatively simple to implement and can cause significant disruption, making them a potent tool for attackers seeking to cause a denial of service.
To mitigate the risk of fork bombs, system administrators can implement resource limits for users and processes, restricting the number of processes that can be created by a single user or within a specific time frame. Regular monitoring of system resources and active processes can also help in detecting and responding to potential fork bomb attacks.