Secondary authentication is an additional verification step applied after or alongside a user’s initial login. It can require another credential, a one-time code, or approval through a separate device. By adding a distinct check, it can reduce the risk that a stolen password alone grants access.
In VPN systems, secondary authentication may be configured for a particular group of remote-access connections. Security depends on both the authentication method and how the service handles requests before verification is complete: a vulnerable pre-login path may still be reachable by an unauthenticated attacker. Defenders should review VPN configuration and vendor advisories, apply security updates, and assess any recommended configuration changes for their impact on access controls.