Which type of malware spreads automatically over networks without user action?

• A. Worm
• B. Trojan Horse
• C. Virus
• D. APT

Answer: (A)

Spreading automatically across networks without user action is the defining trait of a worm. A worm is a self-replicating piece of malware that moves from one machine to another by exploiting vulnerabilities, weak credentials, or misconfigurations, often scanning the network and sending copies to new targets without anyone needing to open a file or run a program. This automatic propagation is what sets worms apart from other malware.

Viruses require some user action to spread, typically by attaching themselves to legitimate programs or files and infecting when those are executed. Trojan Horses rely on users to run something that looks harmless but is malicious. An advanced persistent threat is about a long-term, targeted operation to gain and maintain access, using various techniques—propagation may be part of it, but its primary characteristic is stealth and persistence, not automatic network-wide spread.