Final answer:
A worm is a type of malicious application that can replicate and spread across networks without user intervention or a host application.
Therefore, the correct answer is: option d) worm.
Step-by-step explanation:
A computer worm is a type of malware whose primary function is to self-replicate and infect other computers while remaining active on infected systems. A computer worm duplicates itself to spread to uninfected computers.
Unlike a virus, which requires the infection of an existing program or a Trojan, which requires user interaction to falsely appear as a legitimate program, a worm is designed to replicate itself and spread across networks on its own.
Macro viruses are dependent on software like word processors and spreadsheets to propagate, so they cannot replicate without user intervention either.
The difference between malware and a virus is that malware is the official term used to describe any piece of malicious code (like a worm or a virus) that is designed to infect and cause harm to another person's computer system, regardless of how it attacks the victim's files or how it infiltrates the system.