Here’s a bizarre phenomenon: Some vehicle owners may be storing their key fobs inside of empty potato chip bags overnight. And stranger yet, the practice could hypothetically keep their vehicle from being stolen. That’s one way to “foil” a car theft.

Car thieves are getting more advanced all the time. And while automakers are hustling to stay ahead, even recent model year cars may be vulnerable to theft. One tactic targets keyless entry cars with engine start/stop buttons. This strategy is called a “relay attack.”

In a relay attack, one thief runs up to your front door and holds up a wire loop. This is the antenna of an electronic device engineered to broadcast the signal of a car key fob stored near your front door. The other thief deploys a repeater device near your car. This allows your key and car to “communicate,” sending signals to one another to make your car unlock the doors, then start the engine. Before you know what’s going on, they are driving away in your car.

As a result, savvy car owners are coming up with various ways to block the signal emitted by their key fob. The goal is to keep the thieves from repeating the signal, so the simplest solution is moving your main key–and any spares–as far from the vehicle as possible. Storing them by your bed has the added benefit that you may be able to trigger your car alarm if you see anything suspicious. But some household items can add an extra layer of protection.

To prevent a relay attack, you need to block your car key fob’s RFID signal. The surest blocker is a purpose-built RFID blocking box or pouch. If you are more of a DIYer, several layers of aluminum foil will stop–or greatly reduce–the key fob’s signal. But YouTuber Mad Mods listed several additional options and made the point that potato chip bags are also made of aluminum foil and can go a long way to reduce RFID signals.

I wouldn’t call this a permanent solution, but it’s a great hack in a pinch. Let’s say you are traveling and worried about a neighborhood where you must park overnight. You don’t have time to order an RFID-blocking device or happen to carry aluminum foil in your trunk. You could buy a $1 bag of chips, dump the snacks out, and use it to protect your key fob.

I might turn the entire bag inside out to minimize grease on my key fob. I’ll add that if the end of the bag is open, it won’t work. So you’ll want to roll it up tight. You could rubber band it or put something heavy on it so it won’t unroll at night.

Note that if you need to click a button on your key fob to unlock your car doors, a basic relay attack will not work. So a surefire way to prevent one is to disable your vehicle’s keyless entry feature. But not every automaker allows you to do this.

Next, find out how drivers are preventing a different car theft tactic by chopping their OBD port’s wires, or see more of Mad Mods’ tricks to protect your vehicle from a relay attack in the video below: