MFA (Multi-Factor Authentication)
Definition
Multi-Factor Authentication (MFA) is a security method where a user confirms their identity through two or more verification methods: something you know (password), something you have (phone), or something you are (fingerprint).
MFA is one of the most effective measures against account takeovers. Even if an attacker obtains a password, they cannot log in without the second factor.
Forms of MFA: SMS code (weakest), authenticator app (TOTP), hardware token (YubiKey), push notification. Biometrics are also used.