ANOMALY SENSING ELECTRONIC CONTROL UNIT, VEHICLE-MOUNTED NETWORK SYSTEM, AND ANOMALY SENSING METHOD

An anomaly detection electronic control unit (11) connected to an in-vehicle network includes: a receiver (111) that receives a first communication message indicating speed information of a vehicle including the in-vehicle network and a second communication message indicating peripheral information of the vehicle; a traveling-state determiner (112) that determines a first traveling state of the vehicle based on the speed information and a second traveling state based on the peripheral information; an anomaly determiner (113) that determines, by comparing the first traveling state and the second traveling state determined by the traveling state determiner (112), that the first communication message is anomalous when the first traveling state is different from the second traveling state; and an anomaly processor (115) that executes processing to handle an anomaly when the first communication message is determined to be anomalous.