A security system is provided for a cargo container having a door. An electronic control unit is provided for monitoring the locked status of the door. The electronic control unit is operably communicable with a remote computer terminal. A first software control program is located within the electronic control unit to monitor the locked status of the door. A second software control program is located within the remote computer terminal and is capable of retrieving activity and functions from the first software control program. A protocol is provided to facilitate communication between the electronic control unit and the remote computer terminal.