| 摘要 |
In order to detect a fraudulent action, such as an attempt of invalidating a result of a match-up through a communication in a communication match-up game by changing the setting of a router device, in a communication system, a first terminal device (211) and a second terminal device (221) each attempts to communicate with the terminal device of a communication counterparty. When such attempt has failed, those terminal devices each attempts to communicate with a router device used by the local terminal device of the communication counterparty, and results of these communication attempts are specified in connection information status and the connection information status is transmitted to a server device (231). The server device (231) receives the connection information status, and checks a communication status between the first terminal device (211) and the second terminal device (221), between the second terminal device (221) and a first router device (212) which is connected to the first terminal device (211), and a communication status between the first terminal device (211) and a second router device (222) which is connected to the second terminal device (221), and determines, based on the fact that communicable routes are asymmetric, the presence/absence of a fraudulent action by a user using the terminal device.
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