A traffic monitoring system (10) monitors traffics flowing through a network (100); when an abnormal traffic is detected, identifies an attack source network, a source of an attack, on the basis of attack source information indicating a source device from which the abnormal traffic is transmitted, which is obtained by an analysis of the abnormal traffic, and also identifies an attack destination network, a destination of the attack, on the basis of attack destination information indicating a destination device to which the abnormal traffic is to be transmitted, which is obtained by the analysis of the abnormal traffic; notifies an administrator of the attack source network of the attack source information by acquiring administrator information corresponding to the identified attack source network; and notifies an administrator of the attack destination network of the attack destination information by acquiring administrator information corresponding to the identified attack destination network.