Cheap Faraday Pouches Fail to Block Signals That Let Thieves Steal Keyless Cars

• Independent testing of Faraday pouches, the cheap key signal blockers sold to stop relay theft, found that several popular models let a signal leak through once they had been used and refastened repeatedly.
• Pouches were tested new and again after being tumbled 1,200 times with keys inside to simulate roughly 18 months of daily use, and not every pouch that blocked a signal on day one still blocked it afterwards.
• A well-fitting pouch costs as little as £4, so the difference between a car being protected and a car being vulnerable to relay theft often comes down to which specific pouch a driver bought, not how much they spent.

A £4 pouch that either works or does not

Keyless entry is now standard on the great majority of new cars, and the same technology that lets an owner unlock and start a car without taking the key out of a pocket also creates an opening for thieves using relay equipment. Relay devices capture the signal from a key fob sitting inside a house, boost it, and beam it to a receiver next to the car, tricking the vehicle into behaving as though the key is present. Police and vehicle security experts recommend storing keys in a Faraday pouch, a small case lined with material that blocks the fob’s signal, but not every pouch on sale does what it claims, and the gap between a good one and a poor one is not always visible from the price tag.

How the pouches were actually tested

Auto Express tested a range of Faraday pouches against three keyless cars, first trying to unlock and start each vehicle with a fob sealed inside a pouch held next to the sensor. A pouch that blocked the signal on that first attempt then went through an endurance trial designed to mimic real-world wear, being tumbled 1,200 times with keys inside to simulate around 18 months of being opened and closed twice a day. Foil linings used in cheaper pouches can degrade with repeated handling, so the second round of unlock attempts, carried out after the tumbling, is where the genuine differences between products showed up. A pouch that scores well only when brand new is of limited use to a driver who will be relying on the same pouch a year later.

The results were not sorted by price

The best performer in the test was the Hilka Pro-Craft Faraday Car Key Signal Blocker, a £7.99 twin pack that blocked every signal both before and after the endurance trial, helped by a wide Velcro flap that fastened securely regardless of fob size. A Temu-branded twin pack costing £5.68, working out at £2.84 per pouch, performed almost as well and only lost marks because an overfilled pocket fastened carelessly could allow a faint signal through. The Disklabs KS1, at £24.99 the most expensive pouch tested, blocked every signal throughout but its price kept it off the top spot given how closely the far cheaper options matched its performance.

Further down the results, the picture became more mixed. A Simply RFID Wallet twin pack, at just under £6, leaked a signal slightly once the pouch was completely full, because the flap could not close cleanly around a bulky fob. A near-identical Halfords pouch, sold individually for £4, showed the same weakness, since both products appear to share a manufacturer. An AA-branded pouch costing £11.95 passed every signal test but used a magnet fastener that kept popping open in normal handling, which matters just as much as signal blocking if the pouch cannot be relied on to actually stay shut in a bag or on a hook by the front door.

Why the cheapest option is not automatically the risk

The test results cut directly against the assumption that spending more buys better protection. The most expensive pouch in the test was not the best performer, and two of the cheapest pouches on test, the Hilka and the Temu twin packs, took the top two places. What separated a reliable pouch from an unreliable one was not price but construction detail: the width and quality of the Velcro fastening, whether the pouch has an unprotected outer pocket a key could be slipped into by mistake, and whether the lining held up after well over a thousand open-and-close cycles rather than just on the day it arrived. A driver who buys the wrong £4 pouch has not saved money against a £20 pouch that actually works. They have paid for a product that offers no protection at all while believing their car is covered.

Fit and features matter as much as the lining

The test also highlighted how much ordinary design details affect whether a pouch gets used correctly every single time, which matters because a pouch that blocks every signal in a laboratory test is only useful if the owner actually seals it properly on the way out the door each evening. A wide Velcro flap that fastens easily regardless of whether one key or several are inside performed consistently better across the test than narrower fastenings that required a precisely flat pouch to close cleanly. Pouches with a separate, unprotected outer pocket were flagged as a design flaw rather than a feature, since it is easy to absent-mindedly slip a fob into the wrong compartment and leave it completely unprotected while believing it is safely blocked. A loop or chain for attaching a keyring, offered on some of the pricier pouches tested, adds convenience but made no difference to whether the signal was actually blocked, which is the only feature that matters for security.

Buyers should also be wary of treating a twin pack as double the protection rather than one pouch each for two sets of keys. Households with more than one keyless car, or with a spare fob kept at home, need enough pouches for every fob in circulation, since a single unprotected key left on a hallway table defeats the purpose of protecting the others. Given that a reliable twin pack costs under £8, the economics of fitting out an entire household are modest next to the cost of a stolen car, let alone the increase many insurers apply to premiums once a policyholder has made a theft claim.

What this means alongside other car security measures

A Faraday pouch is one layer in protecting a keyless car, not a complete answer on its own. Steering wheel locks, tracker devices and parking a car where a relay attack is harder to carry out, such as off-street or facing away from a house wall, all reduce the same underlying risk from a different angle. Government has also moved on the tools used to carry out relay attacks and similar keyless theft methods: new offences targeting the possession and supply of car key signal theft devices give police more powers to act before a theft happens rather than only after, a shift covered in detail in our report on new police powers over car key theft devices. None of that removes the value of a pouch that actually works, since it remains one of the cheapest and simplest steps available to any keyless car owner, but it does mean a pouch bought once and never checked again should not be treated as a guarantee.

Drivers who already own a Faraday pouch and are not certain how well it performs can run a simple check themselves. With the key inside the sealed pouch, try to unlock the car by pressing the fob close to the door handle or bringing the pouch near the car. If the car unlocks, the pouch is not doing its job and should be replaced rather than trusted for another year. Given how directly the make and model of pouch affects the outcome, and how little separates a £4 product that works from one that does not, checking which specific pouch performed well in independent testing is worth the two minutes it takes, particularly for anyone driving one of the models most frequently targeted for relay theft.

Sources:

• Auto Express, “Best Faraday bag car key signal blockers 2026”
• Auto Express, “Keyless car theft: what it is, how it works and tips to protect your car”