Can a thief really drive off in your keyless car without ever touching your key, in less time than it takes to make a coffee?
Yes, and this kind of relay theft happens often enough that it is now the single most common way keyless cars are stolen in the UK. It is called a relay attack, and it works by tricking your car into thinking your key fob is sitting right next to it, when it is still on the hallway table inside your house. For anyone researching keyless car theft prevention after a scare, or simply trying to stay ahead of keyless car theft in their area, understanding the mechanics is the first step.
This guide explains exactly how a relay attack works, why some of the advice you have already heard (metal tins, Faraday pouches, parking under a streetlight) only gets you partway there, and what closes the gap in 2026. Where relevant, VMS AutoCare fits TASSA-verified CAN bus immobilisers, including the Scorpion X-Series and CAN-PHANTOM ranges, built specifically to stop the class of attack described below, alongside insurance-approved trackers for drivers who want a recovery layer as well as a prevention layer.
What Is a Relay Attack, and How Does It Actually Work?
A relay attack is a two-person, two-device operation. One person stands near your front door with a signal-amplifying device, close enough to pick up the faint signal your key fob is always emitting, even from inside your house. A second person stands by your car with a matching device that repeats, or ‘relays’, that captured signal to the vehicle. As far as your car is concerned, the real key is present, so the doors unlock and the engine starts.
It is fast. The whole theft process takes about 20 to 30 seconds once the devices are in position. The thieves involved never need to physically touch your key, break a window, or trigger a factory alarm. Devices capable of doing this can be bought online for well under £50, which is a large part of why relay theft has spread so quickly since keyless entry became standard on most new cars.
How Common Is This in the UK Right Now?
Vehicle theft has not eased off. UK vehicle theft has risen by an estimated 74% over the past decade, with relay-style, high-tech methods now cited as the leading route in, ahead of old-fashioned forced entry. Once a car is gone, getting it back is far from guaranteed: ONS figures show 68% of stolen vehicles in the UK went unrecovered in the year to March 2024, up from 56% the year before. If your model regularly appears on lists of the most stolen cars UK-wide, keyless car theft prevention is not something to put off, particularly if it’s one of the keyless SUVs and 4x4s that relay-theft gangs consistently target.
| Statistic | What it tells you |
| Vehicle theft up ~74% over the past decade | This is a structural rise, not a short-term spike |
| 68% of stolen vehicles went unrecovered in the year to March 2024 (ONS) | Recovery is not something to count on by default once a car is gone |
| Relay attacks widely reported as the leading high-tech theft method | Reported consistently across multiple industry sources, though exact percentages vary by source |
Why the Advice You Have Already Heard Does Not Fully Work
Search for “how to stop keyless car theft” and you will get the same five tips everywhere. They are worth doing, but none of them is a complete answer on its own:
- Faraday pouches: a signal-blocking pouch stops the relay if you remember to use it every single night, but counterfeit pouches that do not actually block a signal have been reported on sale, and a pouch does nothing once you are out and about with your keys in your pocket.
- Metal tins or biscuit tins: may partially block a signal, but this is inconsistent and was never designed for the job, unlike a purpose-made pouch.
- Steering locks: a visible deterrent, but they do not stop the electronic exploit itself, only add a physical delay once the thief already has the car unlocked.
- Your car’s factory alarm and engine immobiliser: this is the one that surprises most drivers. A relayed signal looks completely genuine to the car, so the factory engine immobiliser authorises the engine to start. It has no way of knowing the real key is 20 metres away inside your house.
- Parking in a well-lit driveway: reduces opportunistic theft, but a relay attack does not need cover of darkness or an isolated location to work.
Keyless Car Theft Prevention: What Actually Stops a Relay Attack in 2026
The common thread above is that every one of those measures either relies on you remembering to do something every night or trusts the same signal a relay device can copy. Real keyless entry car theft prevention, and genuine keyless car security more broadly, comes from an aftermarket engine immobiliser that checks for authorisation completely independent of the key fob, commonly wired into the vehicle’s CAN bus network.
| Security layer | Stops a relay attack on its own? |
| Faraday pouch | Reduces risk if used every time, but does not cover CAN-based or OBD-port attacks |
| Factory alarm / immobiliser | No – a relayed signal is read as genuine, so the car starts as normal |
| Steering lock | No – visible deterrent only, does not stop the car being unlocked and driven |
| CAN bus immobiliser (e.g. Scorpion X-Series, CAN-PHANTOM) | Yes – requires a separate PIN, tag or app authorisation the relay device cannot copy, so the engine will not start even if the doors unlock |
| Insurance-approved tracker | Adds real-time tracking and recovery support after the fact; ADR-equipped models such as the Scorpion S7 also add a genuine preventive layer, since they immobilise the vehicle for unrecognised drivers |
An engine immobiliser like the Scorpion X-Series or CAN-PHANTOM sits on the vehicle’s own data network and simply refuses to let the engine run until a second, independent step happens, entering a PIN sequence, presenting a tag, or confirming via an app. None of that information travels over the key fob’s radio signal, so a relay device has nothing to copy.
The New Relay-Device Law Is a Step, Not a Full Solution
The Crime and Policing Act 2026, which came into force in April 2026 after first being announced in February 2025, made possession or distribution of relay devices and signal jammers a criminal offence, carrying a maximum sentence of five years. That is a meaningful deterrent, but as several installers covering the change have pointed out, the law restricts supply, while organised theft groups tend to adapt their methods quickly. In practice, that means vehicle-level protection still matters just as much as it did before the law changed, not less.
Immobiliser or Tracker: Do You Need Both?
They solve two different problems, and most of the layered security guides covering this topic in 2026 recommend running both together rather than choosing one:
- An immobiliser (Scorpion X-Series, CAN-PHANTOM) is prevention: it stops the engine starting in the first place, which is exactly what a relay attack is trying to trigger.
- An insurance approved tracker (Scorpion S7, S5, S5+ tracker) is mainly recovery, though ADR-equipped models add a preventive layer too: if a vehicle is ever taken by another method entirely, it gives you and the police a fighting chance of getting it back and can also qualify you for an insurance premium discount, which we cover in detail in next week’s post. Most insurance approved trackers on the market, including VMS AutoCare’s, are Thatcham-categorised, which is the same standard behind proper car security Thatcham accreditation for immobilisers.
Fitted together, you get a car that a relay device cannot start, and a fallback that gives you visibility if anything else is ever attempted.
How VMS AutoCare Approaches Keyless Car Security and Protection
VMS AutoCare fits TASSA-verified CAN bus immobilisers (Scorpion X-Series and CAN-PHANTOM) across Croydon, Purley and the wider Surrey area, alongside insurance approved Scorpion tracker options for drivers who want both layers covered by one installer. Every fitting is carried out by a qualified technician, and the system is matched to your specific vehicle’s CAN bus architecture rather than a one-size-fits-all install, which is what makes the independent-authorisation step actually hold up against a relay attack. The result is keyless car protection that works whether your car is on the drive or a hundred miles from home, backed by genuine TASSA verification and Thatcham-categorised tracking rather than a generic aftermarket fitting.
Let VMS AutoCare Protection Intervene
Relay attacks are quick, cheap for the criminals involved, and specifically designed to slip past the security your car already came with. Faraday pouches, steering locks and careful key storage all help, but the only measure on this list that stops the theft outright is a CAN bus immobiliser that does not trust the key fob’s signal at all. VMS AutoCare fits exactly that, with the Scorpion X-Series and CAN-PHANTOM ranges, plus insurance-approved trackers if you want recovery cover as well as prevention.
Ready to close the gap on your own car? Get in touch with VMS AutoCare today to book a CAN bus immobiliser fitting or ask about combining it with an insurance-approved tracker for full prevention-and-recovery cover.
FAQs
Q: What is a relay attack?
A: It is a method of stealing a keyless car by capturing your key fob’s signal from inside your home and relaying it to the vehicle, tricking it into unlocking and starting as if the real key were present.
Q: How long does it take thieves to steal a keyless car this way?
A: Most reported cases put the whole process at 20 to 30 seconds once both devices are in position, often without the owner noticing anything until the car is already gone.
Q: Does a Faraday pouch fully stop a relay attack?
A: It significantly reduces the risk if used every time your keys are at rest, but it will not help if you forget to use it, and it does nothing against CAN-injection or OBD-port attacks, which is why it is not treated as a complete solution on its own.
Q: Will my insurance still pay out if my keyless car is stolen?
A: Most UK insurers will cover relay theft, but check your policy wording, as some require you to retain and provide all sets of keys and show reasonable care was taken to secure the vehicle.
Q: Does an aftermarket immobiliser actually stop a relay attack, when my factory one did not?
A: Yes, provided it requires a separate authorisation step that does not travel over the key fob’s signal, such as a CAN bus immobiliser like CAN-PHANTOM or the Scorpion X-Series, which a relay device has no way to copy.
Q: Is it illegal to own a relay device in the UK?
A: Since February 2025, possessing or distributing relay devices or signal jammers is a specific criminal offence carrying up to five years in prison, though this has not eliminated the risk to individual vehicles.