Unauthorized control suppression method, unauthorized control suppression device, and onboard network system

An unauthorized control suppression device, connected to a communication channel over which a plurality of electronic controllers exchanges a plurality of frames, the unauthorized control suppression device comprising:

• a receiver that sequentially receives the plurality of frames from the communication channel, the plurality of frames including a control frame that instructs an object of control to perform predetermined control;
• and
• circuitry that, in operation, performs operations including
• determining whether the predetermined control, instructed by the control frame received by the receiver, is to be suppressed, based on a set of frames received by the receiver the set of frames being included in the plurality of frames,
• wherein the set of frames is received by the receiver within a predetermined period preceding a time of reception of the control frame.

An onboard network system including a plurality of electronic control units controllers that exchanges frames, via a network bus, the onboard network system comprising:

• a receiver that sequentially receives the frames from the network bus, the frames including state frames and a control frame, the state frames including information relating to states of a vehicle, the control frame instructing the vehicle to perform predetermined control;
• and
• circuitry that, in operation, performs operations including
• determining whether the predetermined control, instructed by the control frame received by the receiver, is to be suppressed, based on whether a state of the vehicle in a predetermined period preceding a time of reception of the control frame satisfies a predetermined condition,
• wherein the state of the vehicle is identified in the predetermined period preceding the time of reception of the control frame based on a set of the state frames received by the receiver within the predetermined period preceding the time of reception of the control frame.