An authentication mechanism is a security process or technology used to verify the identity of a user, device, or service attempting to access a system or resource. It forms the foundation of Identity & Access Management (IAM) by validating credentials against stored information to confirm that an entity is genuinely who or what it claims to be. Common authentication factors include something you know (passwords, PINs), something you have (security tokens, smart cards), and something you are (biometrics like fingerprints or facial recognition).

These mechanisms serve as the critical first line of defense in cybersecurity, ensuring only verified entities can access sensitive data and protected systems. Organizations typically implement multiple authentication methods—known as multi-factor authentication (MFA)—to strengthen security and reduce the risk of unauthorized access from compromised credentials, phishing attacks, or identity theft.