Which security measure uses two or more authentication methods?

• A. Multi-factor authentication
• B. Authentication
• C. Authorization
• D. Access Control Lists (ACL)

Answer: (A)

Multi-factor authentication strengthens security by requiring two or more authentication methods from different factor categories. This means proving identity using at least two of these groups: something you know (like a password), something you have (such as a token or a phone with an authenticator app), and something you are (biometric data like a fingerprint). The idea is that even if one credential is compromised, the attacker still needs a second factor to gain access.

For example, entering a password and then providing a one-time code from an authenticator app or scanning a fingerprint both count as two factors, fulfilling the requirement. This differs from authentication in general, which is simply the process of verifying who someone is and can be done with a single factor. Authorization is about what an authenticated user is allowed to do, and Access Control Lists specify permissions. So using multiple authentication methods is precisely multi-factor authentication.