Two-factor authentication, or 2FA, is a type of authentication that requires two different factors in order to verify the identity of a user. It is a security measure that is designed to provide an additional layer of protection against unauthorized access to accounts and systems. Two-factor authentication setup might consist of three possible factors: something they know (such as a password), something they have (such as a security token or a smartphone), and something they are (such as a biometric characteristic, such as a fingerprint or a face scan). This makes it more difficult for an attacker to gain access to an account, as they would need to possess multiple factors in order to authenticate. Two-factor authentication is commonly used in online services, such as email and social media, and banking. Multi-factor authentication is a similar concept, but it refers to the use of three or more factors in the authentication process. An example of a popular application that can generate single-use codes to prove identification of a user/device is Authy.