Continuous validation is the process of verifying the identity of users continuously throughout the duration of their access to a system or a network. This provides an extra layer of security beyond initial login verification. Mutual authentication ensures both parties authenticate to each other, but it does not imply continuous checking of the user's identity. Single sign-on allows a user to log in once and access multiple systems without having to re-authenticate, but it is not synonymous with continuous validation. Biometric authentication at the point of login ensures the user is who they claim to be when they first access the system, but without additional mechanisms, it does not provide continuous validation during the session.