threefactor

Three-factor authentication, or 3FA, is an authentication method that requires presenting three separate credentials from distinct factor categories: something you know, something you have, and something you are. By combining three independent factors, 3FA aims to provide higher assurance than password-based or two-factor schemes.

The factor categories commonly used are knowledge, possession, and inherence. Knowledge factors include passwords, PINs, or passphrases. Possession factors cover items such as hardware security keys, smartphones delivering one-time codes, or smart cards. Inherence factors involve biometric identifiers like fingerprints, facial recognition, iris patterns, or voice signatures. In practice, 3FA can use any three factors from these categories, for example a password plus a security key plus a biometric, or a password plus a one-time code plus a fingerprint.

Three-factor setups are designed to resist a broader range of attacks than two-factor methods, including phishing, credential theft, and device loss. They can improve security posture for high-assurance use cases such as banking, enterprise access, and government services. However, 3FA introduces greater complexity, cost, and potential usability friction. Enrollment and recovery flows must be carefully designed, and privacy considerations for biometrics must be addressed. Availability of all factors can also become a challenge if devices are lost or unavailable.

Standards and technologies that support multi-factor authentication—such as FIDO2/WebAuthn for possession and inherence factors, and guidelines from NIST on authentication levels—are commonly leveraged in 3FA deployments. Ultimately, effective 3FA balances strong security with manageable user experience and robust recovery options.