A form of authentication in which a user is granted access only after providing two or more distinct credentials. The first form of authentication is often a password, the other fomrs might be physical tokens, biometric evidence (like a fingerprint), or one-time codes generated by an authenticator. Often referred to by its acronym MFA, the factors fall into three general categories: something one knows (like a password), something one is (a biometric factor), or something one has (a physical token). In MFA the factors should come from different categories: entering two passwords, for example, isn't MFA. The simplest form of MFA is two-factor authentication.