Car theft through relay attacks is one of the fastest-growing security threats in 2026. Thieves use signal amplifiers to extend your key fob’s wireless signal, unlocking and starting your car from outside your home. A Faraday bag for car keys is the simplest, most effective defense against this attack.
In this guide, we’ll cover how relay attacks work, why Faraday bags stop them, and which products offer the best protection for your vehicle.
What Is a Relay Attack?
A relay attack exploits keyless entry systems. Here’s how it works:
- Thief 1 stands near your front door with a signal amplifier
- Thief 2 stands near your car with a relay device
- The amplifier picks up your key fob signal through walls
- The relay device tricks your car into thinking the key is present
- The car unlocks and starts, all without touching your key
This entire process takes under 60 seconds. Modern keyless entry systems on brands like BMW, Mercedes, Audi, Land Rover, and Tesla are particularly vulnerable.
How a Faraday Bag Stops Relay Attacks
A Faraday bag (also called a signal blocking pouch or RFID blocking bag) contains conductive shielding material that blocks all radio frequency signals from entering or leaving. When you place your car keys inside a Faraday bag:
- The key fob’s signal cannot be detected by relay devices
- No wireless communication can reach the key
- Your car remains locked and secure
It’s the same principle used by law enforcement to preserve digital evidence and by military organizations to protect sensitive electronics. For a deeper understanding of the technology, see our guide on how signal blocking bags work.
Best Faraday Bags for Car Keys in 2026
Not all Faraday bags are created equal. Here are our top picks specifically for key fob protection:
1. GoDark Vault Key Fob Faraday Cage
The GoDark Vault is purpose-built for car keys. Unlike soft pouches, this rigid case provides consistent shielding without signal leakage from imperfect closures. Military-grade construction with a simple open/close mechanism.
- Rigid case design (no signal leakage from folds)
- Fits most key fobs including oversized smart keys
- Military-grade shielding material
- Compact enough for a nightstand or entryway bowl
2. GoDark Faraday Bag (Phone + Key Combo)
If you want to protect both your phone and car keys, the GoDark Phone + Key Bundle covers both. The smaller pouch is sized perfectly for key fobs, while the larger pouch handles phones and tablets.
3. Wisdompro Faraday Bag
For a budget-friendly option, the Wisdompro Faraday Bag offers solid signal blocking at a lower price point. Good for everyday use when you need reliable protection without premium pricing.
For a full comparison of all options, check our Best Faraday Bags of 2026 roundup.
What to Look for in a Key Fob Faraday Bag
When shopping for a Faraday bag for your car keys, consider these factors:
Signal Blocking Effectiveness
The bag must block all frequencies used by keyless entry systems (typically 315 MHz in North America, 433.92 MHz in Europe, and 868 MHz for some newer systems). Look for bags that specify multi-frequency blocking.
Closure Quality
The closure is the weakest point of any Faraday bag. Signal can leak through poor seals. Prefer bags with:
- Double-fold closures (two layers of overlap)
- Velcro + magnetic combinations
- Rigid cases with tight-fitting lids
Size and Convenience
A Faraday bag you don’t use is worthless. Choose a size that fits your routine:
- Nightstand use: Rigid cases or larger pouches work well
- On-the-go: Compact pouches that fit in your pocket or purse
- Multiple keys: Larger bags that fit 2-3 fobs for households with multiple vehicles
For a comprehensive breakdown of all features to consider, read our Ultimate Faraday Bag Buying Guide.
How to Test Your Faraday Bag
Always test your Faraday bag before relying on it:
- Place your key fob inside the bag and close it properly
- Walk to your car with the bag
- Try to unlock the car using the door handle (keyless entry)
- Try pressing the unlock button on your car
- If the car stays locked, the bag is working
Test this every few months. Faraday bags can degrade over time, especially soft pouches that get bent and creased repeatedly. Learn more about why Faraday bags stop working and how to prevent it.
Other Ways to Prevent Relay Attacks
While a Faraday bag is the most practical solution, you can layer your security:
- Steering wheel lock: Visual deterrent even if the car is unlocked
- Disable keyless entry: Some cars let you turn off passive entry in settings
- Motion-sensor key fobs: Newer fobs from Ford and others sleep when stationary
- Key fob location: Keep keys away from exterior walls and front doors
A Faraday bag combined with a steering wheel lock makes your car significantly harder to steal than your neighbor’s unprotected vehicle.
Frequently Asked Questions
Do Faraday bags drain key fob batteries?
No. A Faraday bag actually preserves battery life by preventing the fob from constantly responding to signals. Some users report their key fob batteries lasting 20-30% longer when stored in a Faraday bag overnight.
Can I use aluminum foil instead?
In theory, yes. In practice, aluminum foil tears easily, creates inconsistent shielding, and looks suspicious. A proper Faraday bag costs $15-30 and provides reliable, tested protection.
Will a Faraday bag protect my key fob in an EMP event?
Yes. Faraday bags protect against all electromagnetic interference, including EMPs and solar storms. This is the same technology used in EMP-hardened military equipment.
How often should I replace my Faraday bag?
Quality Faraday bags last 3-5 years with regular use. Test yours every few months using the method above. If signal starts leaking through, it’s time to replace.
The Bottom Line
A Faraday bag for car keys is one of the cheapest security investments you can make. For $15-30, you get peace of mind that your keyless entry system can’t be exploited. With relay attacks increasing year over year, this is a simple precaution that every keyless car owner should take.
Browse our complete collection of signal blocking products or read our Best Faraday Bags of 2026 comparison to find the right protection for your needs.