Thieves can clone a car’s key-fob signal with a cheap relay device and drive off in seconds

Modern cars that unlock and start without a key ever leaving a pocket have made driving more convenient, but that same convenience has opened a door for thieves. Using an inexpensive relay device, criminals can capture and extend the signal from a keyless fob sitting inside a house, trick a car into believing the key is nearby, and drive off in a matter of seconds. The attack requires no broken window, no hot-wiring, and often no sound at all.

The technique has spread precisely because it is cheap, fast, and quiet. As more vehicles ship with keyless entry and push-button ignition as standard features, the pool of potential targets has grown, and consumer-protection authorities have taken notice of a theft method that turns a car’s own security system against its owner.

How a relay attack works

Keyless entry systems rely on a short-range radio conversation between the car and the fob. When the fob is close, the car detects its signal and allows the doors to unlock and the engine to start. The system assumes that if it can hear the fob, the key, and therefore the owner, must be right there. A relay attack exploits that assumption by artificially stretching the distance the signal can travel.

In a typical version of the attack, two people work together with small radio devices. One stands near the house, close to where the fob is kept, and captures its signal. That signal is then relayed to a second device held near the car, which rebroadcasts it so the vehicle behaves as though the key is right beside it. The car unlocks and starts, and the thieves drive away. The whole sequence can unfold in seconds, and public guidance on protecting against such schemes is issued through official channels such as the Federal Trade Commission’s consumer alerts.

Why keyless systems are vulnerable

The vulnerability is rooted in the design goal that makes keyless entry appealing in the first place. The system is built to detect the fob automatically and to react as quickly and seamlessly as possible, so the driver never has to fumble for a key. That responsiveness means the car is essentially always listening for the fob and always ready to trust a signal that appears to come from it, without a way to confirm how far away the key truly is.

Relay hardware takes advantage of this trust. The devices do not need to crack any encryption or clone the key’s secret codes; they simply carry the genuine signal farther than it was meant to travel. Because the car receives the authentic communication, just relayed, it has no obvious reason to reject it. That is what makes the attack both effective and difficult to detect in the moment.

Why the tools are cheap and easy to obtain

Part of what makes relay theft alarming is how accessible the equipment has become. The radio devices involved are inexpensive and require only modest technical skill to operate. What was once the province of sophisticated criminals has become a low-barrier method available to a much wider range of would-be thieves. The economics favor the attacker: a small investment in hardware can yield a valuable vehicle, and the risk of being caught in the act is low given how quickly and quietly the theft occurs.

That accessibility helps explain why authorities have flagged the issue in consumer warnings. When a theft technique is cheap to attempt, silent to execute, and applicable to a broad class of vehicles, it can proliferate quickly. Owners of keyless vehicles may not even realize their cars are exposed, since nothing about the theft resembles the forced entry people traditionally associate with stolen vehicles.

Steps that reduce the risk

Because the attack depends on capturing the fob’s signal, most countermeasures focus on blocking or containing that signal when the key is not in use. Storing a fob in a signal-blocking pouch, sometimes called a Faraday bag, can prevent its transmissions from reaching a relay device parked outside. Some fobs can be switched off entirely when not needed, and keeping the key away from windows and exterior walls, where a device on the street could reach it, reduces the chance of interception.

Physical and layered defenses also help. A visible steering-wheel lock or a similar deterrent adds a barrier that a quick relay theft cannot overcome, forcing a thief to spend time and attract attention. Combining a signal-blocking storage habit with an old-fashioned mechanical lock addresses the weakness from two directions at once, and consumer-protection guidance tends to emphasize exactly this kind of layered approach rather than any single fix.

What the threat says about convenience and security

The rise of relay theft is a case study in a familiar tension. Features designed to make life easier often introduce new risks, and keyless entry is a clear example: the same automatic, hands-free convenience that owners value is what the attack turns against them. Security and convenience frequently pull in opposite directions, and a system optimized for seamlessness can end up trusting too readily.

For drivers, the practical takeaway is awareness rather than alarm. Understanding how the attack works makes its simple countermeasures easy to adopt, and blocking a fob’s signal costs little. For the broader conversation about connected devices, keyless car theft is a reminder that as everyday objects grow smarter and more responsive, the assumptions built into their convenience deserve a second look before they can be quietly exploited.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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