‘How can I prevent keyless theft of my Mazda MX-5?’

Alex Robbins is contributing editor at Telegraph Cars where, as well as responding to readers’ queries, he also contributes reviews of new and used cars, together with articles on buying and selling.

His knowledge of the used car market informs his many buying guides relating to the best buys in particular sectors, with an emphasis on value for money. Every week he will answer your questions on buying and selling, as well as solving your car problems, whether consumer or mechanical.

Do you have a motoring dilemma you’d like our expert to solve? For consumer and used car advice, or car faults, email CarsAdvice@telegraph.co.uk and include your subscriber number. This week’s question…


Dear Alex,

My Mazda MX-5 has keyless locking. When at home I put my key in a Faraday pouch and, inside the pouch, I sandwich the key between two blocker cards. I then put the whole lot into the RFID-protected main compartment of a waist bag. Despite all this, when I went out wearing the waist bag, I found that the car still unlocked and the engine started. So how safe from scanners am I and how best can I block the signal?

– DH

Dear D.H.,

You’ve gone to great lengths to protect yourself from scanner theft, which occurs when thieves use electronic devices (called scanners) to mimic the keyless entry radio (RFID) signals of your car, thereby tricking your key into thinking it’s nearby and emitting the all-important signals to unlock and start it. Thieves can then boost these signals back to the car, enabling them to gain entry and steal it.

The usual way of dealing with this is, as you’ve done, to use a pouch with a Faraday cage built into it, which disrupts the radio signal. However, it’s worth remembering two things.

The first is that even with the best protection, most pouches will only dampen the signal, rather than isolate it completely. Your key was probably in very close proximity, and as a result, radio frequency communication between the key and the car was possible even given the faint signal the key was receiving and emitting.

This may mean that when the key is in the pouch, in your house, the signal is too weak to be spoofed from outside.

The second point to note is that not all Faraday pouches are made equal, so you could try another. I’ve no experience with these pouches, but online consumer magazine Carbuyer tested several, and pronounced the Defender Signal Blocker to be the best. At £6, it isn’t really a hardship to give it a try.

You could also add a steering wheel lock. Granted, these are cumbersome to carry around, but if you simply want to prevent theft from outside your house, you could keep the lock in your garage when not in use and only fit it overnight.

While such a lock would be far from tamper-proof, thieves would have to have come equipped to remove it – and the amount of additional time they’d take might be enough of a deterrent to prevent the theft altogether. Such locks are also an effective visual deterrent.


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