What is Computer Worm?

Last Updated : 11 Sep, 2023

A computer worm is a type of harmful software that copy itself and spread from one computer to another without requiring any user intervention. It's like a sickness that can move through a network of computers, searching for weaknesses to infect. Worms often spread through email attachments that may seem safe, but they can actually cause a lot of trouble. Once a computer is infected, the worm can send itself to the person's contacts, using their email account. This way, it keeps spreading to more and more computers.

A computer worm operates by finding vulnerabilities in computer systems and networks. Once it infects one computer, it searches for other computers connected to the same network and spreads to them. If once they enter into the system, worms create copies of themselves and distribute those copies to other vulnerable machines. They cause a variety of problems, including slowing down network performance, consuming system resources, stealing sensitive information, or even damaging and disrupting computer systems.

How do Computer Worms Work?

First, a worm finds a way to enter a computer system. This can happen through security weaknesses like outdated software, weak passwords, or unprotected network ports. It may also use infected external devices, such as USB drives, as a means of entry. Once inside a computer, the worm starts replicating itself. It searches for other vulnerable systems connected to the same network or accessible through the infected computer by scanning IP addresses or probing open ports. The worm carries a payload, which is a malicious component or set of instructions. The worm delivers the payload to the infected system, allowing it to carry out its intended actions. To continue its spread, the worm aims to replicate and infect more systems. It generates copies of itself by using self-replication techniques, where it creates identical or slightly modified versions of its code then it employs various methods to distribute these copies, such as exploiting network shares or sending infected email attachments.

As the worm propagates, it may exploit network protocols and services to reach new targets. For example, it can exploit weaknesses in email programs to send infected messages to contacts in the users address book. Worms have a continuous lifecycle they are constantly searching for new vulnerable targets and adapting to changes. They evolve by incorporating new propagation techniques, updating their payloads, and exploiting newly discovered vulnerabilities. This ensures their ability to infect more systems over an extended period.

Types of Computer Worms

Email Worms: Email worms spread through email attachments or links. They trick people into opening infected attachments or clicking on malicious links in emails. One of the famous example of email worm is "ILOVEYOU" worm. It spread through email in 2000, disguising itself as a love letter attachment. When opened, it infected the recipient's computer and sent copies of itself to the person's contacts.

Network Worms: Network worms move through computer networks by exploiting security weaknesses in network services or protocols. They infect many systems quickly by scanning and copying themselves automatically. The "Conficker" worm is a example of network worm. It exploited vulnerabilities in Windows operating systems and spread rapidly across networks. It infected millions of computers worldwide and caused significant disruptions.

File-Sharing Worms: File Sharing worms target shared folders or peer-to-peer file-sharing networks. They pretend to be normal files and trick users into downloading and running them. Once executed, they can spread to other shared areas or connected computers. The "Napster" worm affected the Napster file-sharing network in the late 1990s. It targeted specific songs and replaced them with infected files

Instant Messaging (IM) Worms: IM worms spread through instant messaging platforms. They send infected links or files to a person's contacts. By tricking users into clicking on these links, they can infect more systems. The "Kelvir" worm was an IM worm that spread through popular instant messaging platforms like MSN Messenger. It sent infected links to a person's contacts, enticing them to click and unknowingly download the worm.

Internet Worms: Internet worms target vulnerabilities in websites, web servers, or web applications. They can infect computers when people visit compromised websites or interact with infected web content. The "Code Red" worm affected web servers running Microsoft IIS in 2001. It exploited a vulnerability and defaced websites. The worm spread by scanning the internet for vulnerable servers and infecting them with its code.