Car theft is a worry, whether you have a £100,000 Porsche on your driveway or a £1,000 Renault Clio. If someone steals your car you’re going to be frustrated, upset and inconvenienced, both financially and in terms of time.
And while the days of thieves hot-wiring your car and driving off into the night are largely behind us thanks to modern immobilisers, more sophisticated forms of car theft still pose a threat. Chief among these is the remote theft of cars with keyless entry and ignition systems.
Office for National Statistics data shows that car theft has risen sharply over the past decade, and various reports suggest that between 50% and 70% of thefts now involve cars with a keyless entry system. With this type of theft – often known as skimming – criminals use relay signals that replicate those that come from your car’s key fob to unlock and start a car, allowing them to thereby steal it.
These are known as Radio Frequency Identification (RFID) signals and fortunately there is a simple, relatively low-tech and fairly cost-effective way to prevent this sort of car theft (sometimes known as a signal extended relay attack or SERA). It’s called a Faraday pouch, and might also be referred to as an RFID signal blocker. These are affordable to buy, yet it could prove to be one of your most valuable automotive car accessories.
Faraday Bags for Car Keys: A Complete Guide
- What is a Faraday Pouch?
- How are Faraday Bags Constructed?
- Which Cars Need to be Protected from SERA Attacks?
- Is My Car Safe if it Doesn’t Have Keyless Ignition?
- What is Being Done to Stop Keyless Car Theft?
- What Else Can You Use a Faraday Pouch For?
- So What About a Biscuit Tin?
- Other Car Security Precautions
What is a Faraday Pouch?
A Faraday key pouch or Faraday bag is a type of compact Faraday cage. The Faraday cage (also sometimes known as a Faraday shield or Faraday box) is an enclosure of conductive material. It works because it diverts the effects of an electromagnetic field around the cage’s conductive material, thus cancelling the field’s effect within the interior of the cage.
Named after scientist Michael Faraday, who invented these cages in the 1830s, Faraday cages are used to protect sensitive electronic equipment from external radio frequency and electromagnetic interference – a bit like airplane mode on your iPhone, only more so.
As a result, using the same principle in a smaller application can help prevent interference with – effectively the hacking of – your car’s keyless entry system. The basic idea? Conceal your keyless fob inside a car key signal blocking pouch and the fob signal can’t be reached by cloning technology, so keyless car theft cannot take place. A simple and cost-effective security system like this could be the difference in whether or not you suffer relay theft.
How are Faraday Bags Constructed?
Car key signal blocker pouches tend to be a composite of some sort of fabric material (cotton, leather or similar) combined with a conductive mesh – often copper or aluminium – which provides the conductive signal-blocking layer. To be effective, a Faraday pouch also needs to insulate the car key fob inside from contact with the conductive material.
Some of these products are more sophisticated than others, but there’s no need to go for a military-grade quality one made of carbon fibre and kevlar. A decent, high-quality Faraday pouch can be bought inexpensively from online retailers such as Amazon, or at your local Halfords. Prices start at less than £5. They are often sold in twin-packs and it’s worth remembering that if you have a spare key it should always be kept in one, too.
Which Cars Need to be Protected from SERA Attacks?
Any car with a remote key fob is susceptible to a SERA attack. However, if your car is locked and unlocked with a button, but you need to insert a key into the ignition to start it, thieves can ‘only’ easily break into your car; they won’t be able to start it and drive away, at least not via SERA attack. However, if your car has a start button, then the thieves may well be able to simply start the car and drive off if they can get a relay signal from the key in your home to your car.
Is My Car Safe if it Doesn’t Have Keyless Ignition?
In a word: no. If a thief can get into your car using a signal relay attack, they can then drive the car away if they have the correct equipment: it does have to be a keyless entry car, but not having keyless vehicle ignition won’t necessarily stop well-equipped criminals. If they can connect to your car’s OBDII port (which garages use to diagnose faults with your car), and if they have the right hardware, they can access your car’s ECU and use it to reprogramme a blank key and steal your car within a few minutes. And an immobiliser won’t stop them.
What is Being Done to Stop Keyless Car Theft?
Keyless car theft has become an increasingly serious problem in recent years, but the government has announced plans to help tackle it.
As it stands, the devices that are used to carry out these crimes aren’t illegal. That’s due to change in 2026, however, when the Crime and Policing Bill that was presented to Parliament in February 2025 becomes law. The bill will make it illegal to posses, import, make, adapt or supply ‘an electronic device for use in theft of a vehicle or theft of anything in a vehicle’. The maximum penalty for the offence will be five years’ imprisonment, an unlimited fine, or both.
What Else Can You Use a Faraday Pouch For?
A Faraday pouch stops car key skimming theft because it stops RFID. This is also how contactless debit and credit cards work, so a Faraday pouch can be used to prevent scammers from identity theft by protecting your contactless cards.
A Faraday pouch also blocks WiFi, GPS and Bluetooth signals, so it’s useful for protecting smartphones, tablets, smart watches and handheld GPS devices from unwanted interference: essentially any electronic devices. It can also be used to protect these devices from an attack by an electromagnetic pulse (EMP) or more general electromagnetic interference (EMI).
So What About a Biscuit Tin?
It’s said that putting your car keys in a biscuit tin can act as an improvised Faraday box. But does this actually work? In theory, anything that creates a sufficiently effective Faraday cage can block Wifi, RFID, Bluetooth, mobile phone and SMS signals, NFC (Near Field Communication) signals, and other radio signals, and therefore protect your car from theft by relay signal. However, simply dropping your keys into a biscuit tin may not provide you much in the way of protection when it comes to blocking your car key signal. It might also crush your biscuits. Which nobody wants.
To make a homemade fob protector more effective, you need a container made of some sort of alloy (rather than tin). Galvanised steel is quite effective, but the metal container itself also needs to shut tightly. Another important point is that the key should either be wrapped with a non-conductive material such as bubblewrap or rubber, or the box should be lined in a similar way. Otherwise, the key can make contact with the metal of the box, effectively creating an antenna. And if you do manage to make an effective one, make sure to keep your spare keys in it as well, because the signals from these can also be picked up by thieves.
Other Car Security Precautions
Of course, if you’ve not got a car with keyless entry or keyless start, then your car could still be at risk from thieves. However, there are several sensible anti-theft precautions you can take:
Keep your Car Keys Away from Doors and Windows
Thieves have been known to use long, thin metal poles poked through letterboxes to literally fish car keyrings from hooks near doors or shelves and tables in your hallway. Keeping your car keys in secure drawers or cupboards well away from your front door will help mitigate this risk. You can also fit particular types of letterboxes with interior covers that prevent this sort of ‘fishing’.
Keep Your Car in a Garage
Obviously, this is only really practical if you happen to have a garage, and if it’s big enough/empty enough to fit your car in. Plus, even if you do have one, you should still practice good car key security… and garage key security for that matter.
Invest in Security Cameras
This won’t necessarily prevent criminals from going after your pride and joy, but smarter thieves will be put off even by the presence of cameras, much as households with dogs tend to be less likely to be the victims of burglary. Systems can range from expensive CCTV security camera set-ups to internet-connected doorbell cameras. And if the worst does happen, then you at least have a better chance of catching the thieves.
Fit Your Car with a Tracker
This certainly won’t prevent your car from getting stolen, but it will vastly increase your chances of getting it back.
Try Old-School Physical Security Devices
A metal gearshift lock or steering wheel lock seems like a brutal approach to vehicle security, but a good-qulality example products can’t be worked around without using noisy, time-consuming and expensive cutting tools. In fact, just having a steering lock or similar fitted could be enough to put thieves off and send them searching after easier victims. No wonder they’re still best-sellers.
Faraday pouch FAQs
Do Faraday pouches really work?
Yes, Faraday pouches really work, and many tests have proven them to effectively block the keyless signal that thieves can use to steal a car.
What is the best Faraday pouch to buy?
The basic function of a Faraday pouch is the same, whether you get a basic version for a few pounds or spend a lot more on a high-end model. Some will give greater shielding than others, however, and as with most things you tend to get what you pay for. It’s worth researching the product details to narrow down which one could be best for your needs – there are lots of online reviews that can help.
Which Faraday pouch is recommended by the police?
A number or Faraday pouches have a ‘Secured by Design’ or ‘Police Preferred Specification’ rating that means they have been independently tested and meet recognised security standards.
