If you don’t take the right precautions, your car could be stolen—without anyone needing your keys. Modern car keys constantly transmit signals, and experts warn that thieves can exploit this to access your vehicle.

So, how can you prevent this?

The simplest method: wrap your keys in aluminum foil. It may sound old-fashioned, but several cybersecurity experts agree it’s an effective and cheap barrier against signal theft. A more convenient option is to use a Faraday bag, which blocks electromagnetic waves in the same way but is designed for daily use.

Moshe Shlisel, CEO of GuardKnox Cyber Technologies and former Israeli Air Force defense engineer, explains: “It’s like a song that plays between a key and car. If someone knows that song, they can open your lock.”

Aluminum foil or a Faraday pouch works by creating a protective shield, preventing hackers from capturing or copying that “song.”

Though it may seem outdated, car thefts using these methods are increasing. Devices for such attacks are easy to buy online, and tutorials are everywhere. The auto industry is aware—and working on stronger, smarter defenses.