Which of the following types of virus is capable of changing its signature to avoid detection?

A polymorphic virus uses a built-in mutation engine to alter its binary signature, encryption routine, or code structure with every infection cycle, ensuring that no two copies produce the same byte-level signature and thus evading traditional signature-based antivirus scanners while preserving its malicious payload.

A boot sector virus infects the master boot record or volume boot record to persist across reboots and execute before the OS loads, but it does not mutate its own signature to evade detection.

A macro virus embeds malicious code within document macros (such as in Microsoft Office files) and spreads through document sharing, but it does not change its own code or signature.

A stealth virus hides its presence by intercepting operating system calls and returning falsified data to security tools, but unlike a polymorphic virus, it does not alter its own binary signature.