Which virus type modifies its code for each replication to avoid detection?

Which virus type modifies its code for each replication to avoid detection?

• A. Mutation engine
• B. Polymorphic viruses
• C. Decryptor routine
• D. Macro virus

Answer: (B)

Mutating code across replications to evade detection is the hallmark of polymorphic viruses. Each time a polymorphic virus infects a new file, it alters its own appearance—usually by encrypting the payload and swapping in a different decryption stub—so the exact byte sequence looks different even though the malicious action remains the same. This keeps signature-based defenses guessing, since there isn’t a single fixed pattern to match. The mutation engine is the mechanism that creates these variations, while the decryptor routine is the decoding step that changes with each new form. Macro viruses rely on embedded macros in documents and don’t inherently mutate in this way, and a decryptor routine alone is just a component, not the virus type. So the type of virus that modifies its code on every replication to avoid detection is polymorphic viruses.

Mutating code across replications to evade detection is the hallmark of polymorphic viruses. Each time a polymorphic virus infects a new file, it alters its own appearance—usually by encrypting the payload and swapping in a different decryption stub—so the exact byte sequence looks different even though the malicious action remains the same. This keeps signature-based defenses guessing, since there isn’t a single fixed pattern to match. The mutation engine is the mechanism that creates these variations, while the decryptor routine is the decoding step that changes with each new form. Macro viruses rely on embedded macros in documents and don’t inherently mutate in this way, and a decryptor routine alone is just a component, not the virus type. So the type of virus that modifies its code on every replication to avoid detection is polymorphic viruses.