An active Windows user session is a logged-in desktop session that is still open and usable on the device. The user has already authenticated, so the system may hold local privileges, unlocked screens, and cached security material that make the workstation ready for immediate use.
This state matters because many attacks target the session rather than the password. If an attacker gains control of an unlocked or still-valid session, they may launch applications, read data, impersonate the user, or reach cloud services that trust the workstation. Defenders treat session state as part of identity security: auto-locking, short idle timeouts, device hardening, and session monitoring reduce exposure. After suspected compromise, teams may need to invalidate tokens, revoke device trust, and force re-authentication, not just reset the password.