Overview: Worm

Quick Definition

A worm is a type of malicious software that replicates itself across networks and systems without requiring user interaction. Unlike viruses, worms are standalone programs that can spread independently by exploiting vulnerabilities in operating systems, network protocols, or applications to move from one computer to another.

Worms typically consume network bandwidth and system resources as they propagate, often causing significant performance degradation or system crashes. Famous examples include the Morris Worm of 1988, which infected approximately 10% of internet-connected computers, and more recent threats like WannaCry and NotPetya, which combined worm-like spreading capabilities with ransomware payloads.

Modern worms often carry additional malicious payloads, such as backdoors, keyloggers, or cryptocurrency miners, making them particularly dangerous. They can spread through various vectors including email attachments, network shares, removable media, and instant messaging platforms. Organizations defend against worms through network segmentation, regular security patching, endpoint protection software, and intrusion detection systems that can identify and block suspicious network traffic patterns associated with worm propagation.