Two-Factor Authentication

A security mechanism requiring two independent proofs of identity — typically something you know (password) plus something you have (authenticator app code, hardware key). Essential for exchange accounts. Hardware-based 2FA (YubiKey, Titan) is significantly stronger than SMS 2FA (SIM-swap vulnerable). App-based (Authy, Google Authenticator) is intermediate. SMS 2FA has been exploited in many SIM-swap attacks against crypto users.