IN-VEHICLE ELECTRONIC SYSTEM, VEHICLE, CONTROL METHOD, AND COMPUTER READABLE STORAGE MEDIUM

An in-vehicle electronic system is mounted to a vehicle. The in-vehicle electronic system includes one or more sensors used to determine a security state of the vehicle, an alarm apparatus configured to issue an alarm when the security state is abnormal, and a first ECU directly connected to the sensor and the alarm apparatus without the intermediation of another ECU and also connected to a plurality of other ECUs, in which the first ECU includes a processor configured to determine a security state based on at least information received from the sensor, and cause the alarm apparatus to operate when it is determined that the security state is abnormal.