If you ask me, hands-free keyless entry is one of the best inventions of the past 100 years. No more digging through my purse or fumbling with keys in the dark in order to open my car doors and start the engine. All I have to do is walk up to my vehicle with the key in my bag or pocket and voil: Im on my way.

Unfortunately, car thieves also love this technology. Using signal boosters, criminals can amplify your key fobs signal in whats known as a relay attack. The car thinks the key is nearby, even if its actually sitting somewhere deep inside your home, allowing thieves to drive off in your vehicle without ever triggering an alarm.

For this reason, some experts have recommended surrounding your car keys with metal in order to block the signal. Some have even suggested storing keys the fridge or microwave , or in a pinch, wrapping the keys in tin foil .

I dont know about you, but hiding my keys behind the eggs and OJ just doesnt seem like a realistic solution. And wrapping them up in foil doesnt strike me as all that secure. So what can you do to protect your vehicle from theft if it employs keyless technology?

How Automotive Relay Attacks Work

Its tough to determine just how many cars are stolen by exploiting weaknesses in the keyless entry, since this type of theft doesnt leave behind any evidence such as broken windows or locks. However, the German General Automobile Club found that 230 of the 237 models it tested, including the Ford Fiesta and Volkswagen Golf, could be easily stolen using relay attacks often in just seconds.

Your vehicles key fob has a long and encrypted passcode that matches the one in your vehicle. When you are in close proximity with your car, your cars computer system will read this code and allow you to unlock your doors, or even start your push-button ignition system, explained Jake McKenzie, content manager at Auto Accessories Garage .

When youre sitting inside your home or office with your keys in your pocket, youre too far away from the vehicle for it to receive that signal. However, it is theoretically possible for thieves to use a signal amplifier that would cause your vehicles computer to recognize your key fob as being closer than it is, McKenzie said.

How exactly? Car thieves will place one piece of equipment near a door or window at your home close enough to pick up your key fobs signal and relay that signal to another piece of equipment near your car (hence the name relay attack), explained Richard Billyeald, Chief Technology Officer for U.K.-based car safety and security organization Thatcham Research . This fools the system into thinking the key is right next to the car, he said. At that point, a thief could unlock and start your vehicle without triggering an alarm.

Using similar technology, its also possible for a thief to capture that signal when youre out and about with the key fob on you (such as walking through a store or parking lot), store the relevant data and then use it to start your car when youre not around.

However, not all vehicles are susceptible to this attack. Those with simple keyless entry only put out a signal when you push the button on your key fob. That means a criminal would have to wait nearby and capture the signal as you push the button, according to Jason David, CEO of Software Portal . Vehicles with remote keyless ignition are riskier because this means the signal is constantly being output, David said.

Should You Be Worried?

Until recently, most modern keyless entry systems were susceptible to relay attacks, Billyeald said. However, many car manufacturers are working to get ahead of the problem.

For example, some manufacturers, such as Ford , are combating relay theft by fitting key fobs with motion sensors that put them into sleep mode if they havent moved in several seconds. It doesnt fundamentally change how the keyless system works, but its a pretty good countermeasure, Billyeald said.

He noted that other manufacturers have begun to implement a new type of technology called ultra wide band , which can be used to achieve the same functionality. That system allows the position of the key to be identified much more accurately, and therefore, isnt susceptible to the attack in the same way.

Finally, manufacturers such as Tesla require a PIN to start the ignition on some models. Though it doesnt prevent thieves from gaining entry to your car and taking items, it at least stops them from driving off in it.

But if your car isnt equipped with these types of additional security measures, there are ways to block your keys signal that dont involve wrapping up your key like an old sandwich. After all, tin foil has been proven to dampen your key fobs signal , but doesnt completely block it since the material lacks density.

The easiest way to prevent this would be to invest in a small RFID-blocking bag , McKenzie said. Known as a Faraday bag (named for the inventor of the original Faraday cage), this fairly inexpensive tool accomplishes the same thing as wrapping your car key in foil, but is much more foolproof (similar technology is used to protect cell phones and credit cards from skimming ).

As for hiding keys in microwaves, fridges and freezers, Billyeald advised against it. Those methods could work, but we wouldnt recommend them especially putting your key in the microwave, as theres a great risk of melting your key or destroying your microwave.

Billyeald agreed that a Faraday bag is the best option for securing your key fob at home, but added that you should always test it out to make sure it works. And dont forget to secure your spare keys in the same way, or your efforts will be for nothing.