Relay attacks seem to be in use in the wild by sophisticated car thiefs, although I'm not sure how commonly. Given general trends, it's probably more common in

Relay attacks seem to be in use in the wild by sophisticated car thiefs, although I'm not sure how commonly. Given general trends, it's probably more common in Europe than in the US. More to your question though, the issue is that proximity key systems rely on the limited radio transmission range. If a thief uses something like an SDR to "amplify" or repeat the transmissions, they can get the car to think the key is much closer than it is... and potentially unlock the car in your driveway by "using" your key fob inside your house. A faraday pouch makes this very difficult by significantly attenuating the signal from the key fob.