With Sametime 8.5.2, we've introduced a great new security feature, "managed access," that lets people join your meeting rooms only when you or a room manager is there.
You can select this option either when creating a new meeting room or by changing the room settings of an existing meeting room.
This picture shows where this setting appears when you create a new meeting room:
This same feature is available for meetings accessed from a web browser:
People who try to join your meeting when you're not there are put in a "waiting room", and they must wait until you're there before they can see any content in the room.
Use this feature whenever you don't want people in your meeting room when you're not there!