What characterizes a worm in the context of malware?

A worm is a type of malware characterized by its ability to replicate itself automatically without the need for user intervention. This distinguishes worms from other types of malware, such as viruses, which often require action from a user (like opening a file or running a program) to spread. Worms take advantage of vulnerabilities in software or network settings to propagate across systems, making them particularly dangerous as they can quickly infect large numbers of devices without any human action.

The other choices describe characteristics associated with different types of malware or behaviors. For instance, some types of malware, like trojans, are often disguised as legitimate software to trick users into downloading and installing them. Options related to encryption for ransom pertain to ransomware, which encrypts files and demands a payment for decryption. Therefore, the defining characteristic of a worm is its capability to self-replicate and spread independently.