What defines a worm in the context of malware?

A worm is specifically defined in the context of malware as a type of self-replicating software that is capable of spreading independently across networks without requiring user intervention or consent. Worms exploit vulnerabilities in software or operating systems to propagate themselves, often leading to significant damage by consuming bandwidth, slowing down systems, and creating vulnerabilities that other types of malware can exploit.

The essence of a worm's functionality lies in its ability to autonomously replicate and distribute itself, distinguishing it from other forms of malware. For example, while viruses may require a host file to spread and may depend on user actions (like opening an infected email attachment) to propagate, worms can spread through network connections automatically.

The other choices represent different forms or characteristics of malware but do not accurately capture the unique behavior and characteristics of worms. For instance, malware that performs desired functions may relate to adware or legitimate software misused for malicious purposes, while software that disguises itself as harmless refers more closely to Trojans. Lastly, malware that restricts access to a victim's computer pertains to ransomware, which is also distinct from the autonomous spread characteristic of worms.