Illegal data detection device, communication system and illegal data detection method

摘要

PROBLEM TO BE SOLVED: To detect a message from a false device crawling into communication system by masquerading as an authorized device in the communication system having a plurality of devices.SOLUTION: An unauthorized data detection device transmits a message and receive a message at a second time interval obtained by elongating a first time interval with predetermined frequency while transmission of the message is being periodically performed at the first time interval by the device transmitting the message out of a plurality of devices. The unauthorized data detection device comprises: a reception section receiving the message; and a control section determining the message received by the reception section to be the message transmitted from the device masquerading as the device transmitting the message when timing when the message is received by the reception section is timing other than timing when the message transmitted at the second time interval is received in the case where the timing is determined to be the timing when the message is transmitted at the second time interval.