COMMUNICATION APPARATUS, UNAUTHORIZED COMMUNICATION PREVENTING METHOD, AND UNAUTHORIZED COMMUNICATION PROGRAM

摘要

[PROBLEMS] To prevent unauthorized use of a portable telephone even if the portable telephone is stolen during roaming. [MEANS FOR SOLVING PROBLEMS] A communication device capable of communication through a network is characterized by comprising a selection means for selecting a network which is used for the communication with other communication devices and is connectable, a distinguishing means for distinguishing whether or not the current time is within the usable period of the selected network, and a prohibiting means for prohibiting the communication with the other communication devices through the selected network if the current time is out of the usable period.