When drivers return home and slip their car keys into the microwave, it’s not forgetfulness; it’s a deliberate attempt to outsmart thieves. The trend targets a vulnerability in vehicles equipped with keyless-entry and push-button-start systems. These cars are designed to unlock and start when the basic fob is nearby, but that convenience can also be exploited in relay attacks.
A microwave’s conductive interior and mesh door are designed to contain electromagnetic energy during cooking. With the door closed, the appliance may also reduce some wireless signals, but it is not a purpose-built or dependable way to shield a basic fob. Its performance depends on the appliance’s construction and condition, including the door seal, as well as the radio frequency involved. A purpose-made signal-blocking pouch or box is designed for this task and can be checked against the specific vehicle.
How Relay Attacks Work
Relay attacks exploit the proximity checks used by keyless systems. One device near the home picks up or extends communication from the fob, while another near the vehicle relays the signal. The car can then interpret the fob as nearby and unlock or start, without a thief obtaining the physical basic or breaking a window. Captain Alan Muench of the Ledyard Police Department has described the equipment as a “relay or signal enhancer.” Cars parked near homes may be more exposed when keys are kept near exterior doors or windows, especially if the vehicle is in a driveway or on a nearby street.
Germany’s automobile club ADAC has tested more than 800 keyless-equipped vehicles. In the assessment cited in reporting on its findings, almost half could be unlocked using an artificially extended basic signal, while roughly one in three could also be started. These figures describe different outcomes, unlocking and starting, and show why the results should not be reduced to a single share of cars that “resisted” an attack. The Spanish traffic authority DGT has also flagged keyless entry as a target for car thieves.
The Microwave Trap: More Risk Than Reward
The microwave trick is not foolproof: whether it attenuates a fob’s signal depends on the appliance and the frequency used. It also creates an avoidable household hazard. If someone switches on the microwave while the fob is inside, metal components can interact with the microwave energy, potentially causing arcing or damage; heat can also harm the fob’s battery and electronics. A microwave should never be operated with a basic fob or another metal-containing object inside. Even when switched off, it is not a reliable storage solution.
Safer Alternatives: Faraday Pouches and Smart Habits
Police guidance recommends keeping an unused fob in a signal-blocking bag or box, storing it away from doors and windows, and checking that the enclosure works with the particular vehicle. One practical check is to leave the fob inside and see whether the car can still be unlocked. If the vehicle responds, the pouch or box is not blocking the signal effectively.
Layered precautions can address risks that a signal-blocking pouch cannot. Drivers can consider parking in a garage or using a steering-wheel lock. Protecting the vehicle’s onboard diagnostic (OBD) port adds another safeguard. A Faraday pouch helps counter relay attacks, but it does not prevent other methods, such as entering the vehicle and programming a blank basic through the diagnostic port. Some newer fobs stop transmitting when stationary, and some models allow the fob to be disabled; availability depends on the vehicle, so owners should check their model’s instructions. Systems using ultra-wideband (UWB) technology can more accurately assess a basic’s proximity, but features vary by vehicle.
Everyday Security and Emergency Risks
Protecting a vehicle is best approached through several measures rather than a household storage trick. Small decisions about where keys are kept can affect both security and safety. A recent report on why leaving keys in the door overnight can hinder emergency response highlights how everyday choices about basic storage can have consequences beyond the immediate concern.
