The present invention provides a method and system for securing a computer. The method includes providing a zone of authorized operation for the computer; determining if a possessor of the computer is authorized to have possession when the computer and the possessor leaves the zone of authorized operation and pass through a portal; and allowing continued access to the computer without requiring a password if the possessor is authorized. The method and system is transparent to the possessor and provides no advantage in hiding the computer from the portal. This method and system may be easily applied in a corporate environment and is particularly apt for securing mobile computer systems.