Method for sensing fraudulent frames transmitted to in-vehicle network

An in-vehicle network system, comprising:

• a plurality of first electronic control units that communicate with each other via one or more networks;
• a second electronic control unit connected to the one or more networks;
• a third electronic control unit that is one of the plurality of first electronic control units, different than the second electronic control unit, and detects whether or not a state of a vehicle satisfies a predetermined condition;
• and
• the third electronic control unit that, upon detecting whether or not the state of the vehicle satisfies the predetermined condition, transmits a switching instruction message to the second electronic control unit,
• wherein the switching instruction message, which is transmitted to the second electronic control unit, causes an operation mode of the second electronic control unit connected to the one or more networks to be switched between a first mode in which a detecting process for detecting a fraudulent message in the one or more networks is performed and a second mode in which the detecting process is not performed.

A fraud-detecting electronic control unit for connection to a plurality of first electronic control units via one or more networks, the fraud-detecting electronic control unit comprising:

• one or more memories;
• and
• circuitry which, in operation:
• detects whether or not a state of a vehicle satisfies a first condition or a second condition;
• and
• causes, upon detecting, in the detecting, whether or not the state of the vehicle satisfies the first condition or the second condition, an operation mode of the fraud-detecting electronic control unit to be switched from:
• a first mode in which a detecting process for detecting a fraudulent message in the one or more networks is performed to a second mode in which the detecting process is not performed, upon detecting, in the detecting, that the state of the vehicle satisfies the first condition;
• and
• from the second mode to the first mode, upon detecting, in the detecting, that the state of the vehicle satisfies the second condition,
• wherein at least a part of the circuitry is included in a third electronic control unit, the third electronic control unit being one of the plurality of first electronic control units and different than the fraud-detecting electronic control unit and detecting whether or not the state of the vehicle satisfies the first condition or the second condition,
• in the causing, upon detecting whether or not the state of the vehicle satisfies the first condition or the second condition:
• the third electronic control unit transmits a switching instruction message to the fraud-detecting electronic control unit;
• and
• the fraud-detecting electronic control unit, to which the switching instruction message is transmitted, switches the operation mode.