zweiFaktorAuthentifizierung

ZweiFaktorAuth, commonly referred to as two-factor authentication (2FA), is a security mechanism requiring two distinct authentication factors to verify a user's identity. It adds a second layer of protection beyond a single password by requiring verification from two different sources.

The two factors typically come from three categories: something you know (a password or PIN), something you have (a device or token), and something you are (biometrics). 2FA combines these categories to reduce the risk of unauthorized access if one credential is compromised. Common implementations include codes sent via SMS, time-based one-time codes generated by authenticator apps, push-based approvals on a registered device, and hardware security keys that use standards such as FIDO2/WebAuthn.

Standards and technologies underpinning 2FA include HOTP and TOTP, which are designed for one-time codes generated by apps, and the WebAuthn/FIDO2 framework that enables phishing-resistant hardware authentication. Many online services support a mix of these methods, often offering recovery codes and backup options for account access if a primary method is unavailable.

Benefits and limitations: 2FA greatly reduces risk from password theft but is not foolproof. Phishing techniques can target users of certain 2FA methods, SMS-based codes are vulnerable to SIM swapping, and lost devices or forgotten backup codes can hinder access. Employing phishing-resistant methods and robust recovery options improves security, while user education and consistent enforcement help maximize effectiveness.

Deployment considerations include selecting resistant methods, providing clear enrollment and recovery workflows, and balancing security with user convenience. 2FA remains a widely adopted, effective layer of defense in both consumer and enterprise environments.