Multi-factor authentication

Multi-factor authentication (MFA) is an authentication method in which the user has to present more than one type of evidence to a system in order to be authenticated.

Most commonly, three different types of evidence (or factors) are distinguished:

• Something you know, such as a password or PIN
• Something you have, such as a cellphone or a hardware security token
• Something you are: a biometric such as a fingerprint

If an authentication system requires the user to provide more than one of these factors in order to authenticate, then it is a multi-factor system.

For example, the system might ask the user for a password as well as a code generated by the authenticator app on their phone.