Which of the following is a common type of malware?

• A. Firewall
• B. Encryption
• C. MFA
• D. Virus

Answer: (D)

A virus is a common type of malware because it’s a malicious program designed to replicate and spread by attaching to legitimate executable files, moving from one system to another and often causing damage along the way. This propagation behavior is what makes it a classic example of harmful software. The other options aren’t malware: a firewall blocks unauthorized access, encryption is a method to protect data, and MFA (multi-factor authentication) strengthens login security. So the answer that describes a spreading, damaging program best fits the question.