You walk to your car, and you raise your key. Press a button, and the doors unlock. Perhaps the lights flash; maybe there’s a welcoming “boop BOOP!” For millions of drivers, this habit is automatic. There’s no need to put the key in the ignition anymore.

It’s certainly convenient. However, you may also be inviting high-tech car thieves who can jack your car and drive away in seconds, without so much as setting off an alarm.

Want to be shocked? Tap or click here to watch a video showing thieves stealing a car in about one minute.

Your key fob uses an electronic signal, and newer models don't even require you to press a button. Just approach your car, and the doors will unlock automatically. In some vehicles, the engine will also turn on.

If you have a true keyless car model, thieves can intercept the signal. How do they do it? Understanding the mechanics of a “car hacking” can help you prevent it.

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How your car's security system works

Inside your key fob, there’s a tiny computer chip. This chip is programmed with a unique code that it sends to your car's security system. The car also has a chip, which uses the same algorithm to generate codes. Put simply, if the codes match up, then the car opens.

How criminals attack #1

For the past couple of years, manufacturers have learned that this chip technology has programming flaws, and skilled hackers can use this vulnerability to unlock millions of vehicles.

This was a frightening surprise. Each key fob/car security pair is unique, and each one can create billions of codes. But Researchers at Radboud University in the Netherlands and the University of Birmingham found that by intercepting the wireless signal twice, they could narrow down the possible combinations from billions to just 200,000. After that, a computer can figure out the code in just half an hour and unlock the car.

In a real-world application, a thief could sit on a street gathering wireless signals as car owners enter and exit their vehicles. Then, they could steal many cars.

Still, that takes a skilled car thief or hacker to carry out this kind of attack, so the odds of it happening to you are slim. However, thanks to always-on key fobs, there's another risk that's much more likely to happen.

How criminals attack #2

Always-on key fobs present a severe weakness of your car's security. As long as your keys are in range, anyone can open the car, and the system will think it's you. That's why newer car models won't unlock until the key fob is within a foot.

However, criminals can get relatively cheap relay boxes that capture key fob signals up to 300 feet away, and then transmit them to your car.

In other words, your keys could be in your house, and criminals could use the relay box to walk up to your car and open it. Fortunately, there are some simple steps you can take to keep hackers from stealing your signal.

Steps to stop car thieves

There are a few easy ways to block criminals' amplified signals. You can buy a signal-blocking pouch that can hold your keys, like a shielded RFID blocking pouch.

1. Stick in the fridge. The free option is to use your refrigerator or freezer. The multiple layers of metal will block your key fob's signal. Just check with the fob’s manufacturer to make sure freezing your key fob won't damage it.

2. Place in your microwave oven. If you're not keen to freeze your key fob, you can do the same thing with your microwave oven. The metal frame should work as well as your refrigerator. Here, though, it’s vital that you don’t turn your microwave on, as you could cause serious damage and even start a fire.

3. Wrap your key fob in foil: This one is tricky. First, you’ll have to convince your friends that you haven’t fallen for some wacky conspiracy theory. More importantly, wrapping your fob in tin foil may hamper your ability to use it. But the tactic should prevent hackers from stealing your signal, and you can even find a small box and line it with foil, just for storage purposes.

4. Get an RFID blocker: This kind of signal stealing isn't just a problem for car key fobs. Newer passports and other identification contain radio frequency identification chips. Criminals can use a high-powered RFID reader to steal your information from a distance. You don't need aluminum foil, however. You can invest RFID-blocking wallets, purposes, and passport cases.

Key fob hacking isn't the only danger to modern cars. Learn how hackers can take control of cars through the entertainment system and other avenues of attack.

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Learn about all the latest technology on the Kim Komando Show, the nation's largest weekend radio talk show. Kim takes calls and dispenses advice on today's digital lifestyle, from smartphones and tablets to online privacy and data hacks. For her daily tips, free newsletters and more, visit her website at Komando.com.