A destructive computer program that masquerades as a useful application is called a

A Trojan is a destructive program that masquerades as a useful application to trick the user into running it.

A virus attaches itself to files and spreads when those files run, which differs from disguising itself.

A worm self-replicates across networks without needing a host program.

Firmware is legitimate software stored on a device, not malware.

A Trojan does not self-replicate like a virus or worm.

Trojans are often used to open a backdoor for attackers.