Glossary
Multi-Factor Authentication (MFA)
Multi-factor authentication combines something a principal knows (a password), something it has (a hardware key or a device generating one-time codes), or something it is (a biometric) — so that compromising one factor alone does not compromise the identity. A stolen password without the second factor is not enough to authenticate.
Not all second factors offer the same protection. A code sent by text message can be intercepted or redirected through carrier-level attacks; a hardware key that never transmits a secret over the network is considerably harder to defeat remotely. Choosing a factor is itself a security decision, not just a checkbox.