How is multi-factor authentication defined?

Multi-factor authentication (MFA) is defined as a security mechanism that requires two or more forms of verification before granting access to a system or resource. This approach enhances security by combining different types of authentication factors, which are generally categorized into three types: something you know (like a password), something you have (like a security token or a smartphone), and something you are (like biometric data such as fingerprints or facial recognition).

By requiring multiple forms of verification, MFA significantly reduces the risk of unauthorized access. Even if one factor (such as a password) is compromised, an attacker would still need to provide additional factors, making it much harder to gain access.

The other options describe methods that do not align with the comprehensive nature of MFA. A single verification method does not provide the layered security that multiple factors do. Relying solely on biometrics or only verifying identity through email lacks the redundancy and security enhancements that MFA aims to provide. Thus, recognizing the value of multi-factor authentication as a combination of various verification methods is crucial for a robust security strategy.