What is multi-factor authentication (MFA)?

Multi-factor authentication (MFA) is a security mechanism that requires multiple verification factors to gain access to a resource, such as an application, online account, or virtual private network. The primary purpose of MFA is to enhance security by requiring users to present two or more distinct forms of verification. These factors typically fall into three categories: something you know (like a password), something you have (like a smartphone or hardware token), and something you are (like a fingerprint or facial recognition).

The use of multiple factors significantly reduces the likelihood of unauthorized access, as it is much harder for an attacker to gain access without all the required credentials. For instance, even if a password is compromised, the user would still be required to provide a secondary form of verification.

In contrast, the other options provided do not accurately describe the concept of MFA. A single method of user authentication only involves one verification factor, which does not provide the additional security that MFA offers. An encryption technique for database security pertains to data protection and storage rather than the authentication process itself. Lastly, identity verification by email is a method of authentication but typically relies on a single factor (accessing the email account) and does not incorporate multiple factors, thus falling outside the definition of MFA.