Hooded thief tries to break the car's security systems with tablet. Hacking modern car concept

Car owners warned of another theft-enabling relay attack

Tesla owners are no strangers to seeing reports of cars being tampered with outside of their control. Back in 2021, a zero-click exploit aided a drone in taking over the car’s entertainment system. In 2016, we had a brakes and doorsissue. 2020 saw people rewriting key-fob firmwarevia Bluetooth. Andin January this year, a teen claimedhe had managed to remotely hack into 25 Tesla vehicles.

This time, we have another Bluetooth key-fob issuemaking waves. Although there is a Tesla specific advisory, there are also advisories for this issue generally and a type of smart lock.

Bluetooth Low Energy and keyless entry systems

The researchers who discovered this issue are clear that it isn’t “just” a problem for Tesla. It’s more of a problem related to the Bluetooth Low Energy (BLE) protocol used by the keyless entry system. Bluetooth is a short-range wireless technology which uses radio frequencies and allows you to share data. You can connect one device to another, interact with Bluetooth beacons, and much more. Bluetooth is a perfect fit for something as commonplace as keyless door entry.

As the name suggests, BLEis all about providing functionality through very low energy consumption. As BLE is only active for very short periods of time, it’s a much more efficient way to do things.

The relay attack in action

Researchers demonstrated how this compromise of the keyless system works in practice. Though light on details, Bloomberg mentions it is a relay attack. This is a fairly common method used by people in the car research realm to try and pop locks.

To help describe a relay attack, it’s common to first explain how a Man in the Middle(MitM) attack works:

In cybersecurity, a Man-in-the-Middle (MitM) attack happens when a threat actor manages to intercept and forward the traffic between two entities without either of them noticing. In addition, some MitM attacks alter the communication between parties, again without them realizing.

For relay attacks, think of two people (or one person with two devices) sliding their way into the device-based communication. Some of the diagrams I’ve seen explaining this attack can be a little confusing, but this video explanation is perfect:

As you can see, two people approach the car. One pulls the handles to trigger the car’s security system into sending out a message. “Are you the owner of this car, are your keys the correct keys for this vehicle?” The authentication challenge is beamed out into the void. The second person is standing by the house with a device.

People often leave their car keys close to the front door. As a result, the keys will be within range of the second person’s device. It takes the fob’s response and beams it back to the criminal by the car. The device in their hand relays the fob’s authentication confirmation to the car and the door unlocks. They then repeat this process a second time. This is to fool the car into thinking the keys are present, at which point they’re able to drive away.

A gear-shift in criminal perspective

Criminals are after maximum gain for minimum effort. They don’t want to attract attention from law enforcement. The sneakier they can be, the less commotion they cause, and the better it’s going to be for them in the long-term.

Think about how seamless a relay approach is to car theft. It’s quick, it’s easy, and it’s completely silent. Consider how much money a professional outfit pulling these car heists can generate. The alternative is messy break-ins, noise, rummaging for keys in a house full of screaming people and barking dogs. Not to mention a significantly increased chance of being caught. If you were a career criminal, which approach would you favour?

A problem which refuses to go away

Relay attacks on cars have been around for several years now. Stolen vehicles are the go-to example of relay attacks if you go looking for more informationon the technique. Advice for avoiding relay attacks is widespread, from keeping keys away from the front door (which you should do anyway) to placing them in a signal-blocking bag.

For the Tesla specific attack, a relay device was placed “within roughly 15 yards” of the smartphone/key-fob, with the other plugged into a laptop close to the vehicle. You can see more information about the more general forms of attack here.

The article mentions that there’s no evidence of this Tesla tomfoolery having happened in the wild. Even so, relay attacks can and do take place. If your car operates a keyless system, take this latest report as a heads-up to ensure your vehicle is safe from attack no matter the make or model.


Christopher Boyd

Former Director of Research at FaceTime Security Labs. He has a very particular set of skills. Skills that make him a nightmare for threats like you.