Which term describes viruses that rewrite their entire code during each infection, making each copy unique?

• A. Metamorphic viruses
• B. FAT virus
• C. Shell virus
• D. Zombie

Answer: (A)

Metamorphic viruses rewrite their entire code during each infection, producing a completely new, unique copy every time. By morphing their instructions and structure, they carry out the same payload but look different at the binary level, which makes pattern- or signature-based detection far more difficult. This is distinct from other types: a FAT virus refers to where the virus infects (on FAT file systems), not how its code changes across infections; a shell virus attaches to or uses a command shell to execute, without re-creating its entire codebase each time; a zombie is a compromised host in a botnet used for tasks like DDoS, not a virus that continuously rewrites itself.