Which timeout behavior starts counting down from the moment the user authenticates?

The timeout behavior that starts counting down from the moment the user authenticates is known as "Hard" timeout. In this context, a hard timeout defines a fixed duration of time that a user session can remain active once the authentication has been successfully completed. This timer begins immediately after the user logs in, regardless of any subsequent activity or inactivity. Once the duration expires, the session will be terminated, requiring the user to authenticate again to regain access.

In contrast, a new session timeout typically applies to the establishment of a session but may not necessarily count down from the authentication point itself. An idle timeout specifically relates to how long the session can remain inactive before it's closed, which does not begin counting until there is an absence of user activity after authentication. A session limit is more about the total number of allowed sessions or connections rather than a countdown related to authentication activity. Thus, in the context of this question, hard timeout is the only option that fits the given criteria accurately.