A ___________ is a program that poses as a useful or legitimate program, but turns out to be malicious code.

A worm is a standalone malicious program that replicates and spreads autonomously across networks without user intervention, unlike a Trojan which relies on deception for initial execution.

A Trojan Horse is specifically designed to appear benign or useful to a user, such as a game or a utility, but contains hidden malicious functions that activate upon execution, precisely fitting the description.

A logic bomb is a piece of code that executes a malicious function when specific conditions are met, often embedded within legitimate software, rather than being an entirely deceptive program itself.

A polymorphic virus is a type of virus that changes its signature to evade detection, but it still functions as a virus by attaching to and infecting legitimate programs, not posing as a useful program itself.