A Rock continuously monitors the space in front of the door. First it detects people, next it detects faces, finally it detects the intent of a person to pass through the door and then authenticates the face of that person. Since the Rock detects people, it also can determine which person or people pass through the door. If a person other than the authenticated people passes through the door, the Rock asserts a Tailgating Alert. This alert is reported to the admin portal and can optionally be reported to the ACS via Wiegand or OSDP.