NIST SP 800-63-4 is the current U.S. digital identity guideline suite for identity proofing, authentication, and federation. It helps organizations decide how to verify a user at enrollment, how to authenticate them at login, and how identity should be trusted across connected services.
In cyber security, it matters because weak identity controls are a common attack path. The framework favors phishing-resistant authentication, such as cryptographic authenticators bound to the real service, so stolen passwords or one-time codes are less useful to attackers. It also highlights the need to review session risk over time and to secure recovery and help-desk flows, since attackers often target those weaker paths. In practice, SP 800-63-4 supports stronger Zero Trust identity decisions in cloud, SaaS, and federated environments.