The simple hack thieves can use to unlock and steal your car

You may be hearing from friends, or reading posts from neighbors on Nextdoor about how ‘I must have left my car unlocked last night…’ They describe how they’re so careful, and they never leave their car unlocked. But last night someone got into it without breaking in, rifled through it, and stole any valuables left inside. Then, several other neighbors will chime in and say that they also, uncharacteristically, left their car unlocked last night. But did all of these diligent people on the same street really happen to leave their cars unlocked the same night?

No. They probably didn’t. It’s likely that thieves used a simple hack to get into their cars without leaving any sign of a break-in.

The devices that enable thieves to do this are called signal boosters. They’re a simple hack thieves can use to steal your car. They can generally be assembled with less than $50 worth of materials. With instructions on the internet, virtually anyone can build them. They’re used by high-level car thieves and high school students alike.

How it works

Most cars with remote key fobs basically work through sending signals back and forth. In normal (legitimate) circumstances, when you get near your car, the remote entry system in the car detects that the key is near, and it sends out a signal to the key. The key, in return, sends a response, and the system unlocks the car. (It’s a little bit like saying a password to get into a speakeasy; the system is asking for the word, and the key fob essentially responds with the correct word.) Normally this is fine, because it’s you, with the fob, walking up to your car.

A simple hack thieves can use to steal your car
The larger device is placed near the key fob, and the smaller one near the car.

But when thieves are trying to steal the car, they use signal amplifying devices to trick both the entry system and the key fob into thinking they’re close to each other. So your key fob could be inside your house, and your car in the driveway. One thief holding a device gets near the fob, and the other stands near your car. The devices have longer-range capability, so they amplify the car’s password request to the key, and the key’s response. The whole exchange happens just like it would if the fob were actually close to the car. And the door opens. And in cars with keyless ignition (like start buttons), the car can even be started this way.

It’s easy to prevent

The good news is that, as advanced as this hack is, the solution is very simple. You just need to block your key fob’s signal when you’re not using it to open or drive your car. There are a few ways to do this. Some people recommend putting it in your refrigerator or freezer. That will work, because the airtight metal walls will block the signal. But the moisture isn’t ideal for the longevity of your key fob’s circuit board or its battery.

You also might see recommendations to use aluminum foil (just like some people use for hats, to block alien mind control signals). But wrapping your fob in foil can actually allow the signal to ‘leak’ out, unless you get it just right. Which is a hassle, for something you’ll be doing every time you get home.

The best solution is to buy a shielded bag, sometimes called a Faraday Bag. It’s lined with material that blocks your fob’s signal. It’s designed to be easily folded and secured in a way that will make sure no signals can get in or out. For tips on preventing lower-tech types of car theft, check out our article on car anti-theft devices.

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