Multi-Factor Authentication (MFA)
Also known as: Two-Factor Authentication · 2FA
Definition
Multi-Factor Authentication (MFA) is a security mechanism that requires two or more distinct factors from independent categories (something you know, have, or are) to verify identity.
The three classical factor categories are: knowledge (password, PIN), possession (phone, hardware token, smart card), and inherence (biometric — fingerprint, face, voice). True MFA requires factors from different categories — combining two passwords is not MFA.
Not all MFA is created equal. SMS and voice OTP are MFA but trivially phishable. TOTP authenticator apps are stronger. Push with number-matching is stronger still. FIDO2 / passkeys are phishing-resistant. Auditors increasingly distinguish "any MFA" from "phishing-resistant MFA" — the latter is the baseline for privileged access.