A device for detecting nefarious communication signals in a vehicle includes a detection support logic, a nefarious logic, a filtering circuit, and a microcontroller. The device receives a measurement signal from the detection support logic. The device determines a characteristic of an alternating current (AC) signal during communication at a first time on a wiring harness of the vehicle based on the measurement signal. The device determines the characteristic of the AC signal at a second time based on the measurement signal. The device determines that the characteristic measured during the first time differs from the characteristic measured during the second time. The device transmits a blocking signal to the nefarious logic to filter a frequency band of a communication conductor of the wiring harness in response to the determination that the characteristic measured during the first time differs from the characteristic measured during the second time.