Faraday Bags: Complete Phone Isolation
A Faraday bag is a pouch lined with metallic mesh that blocks all electromagnetic signals. When your phone is inside, it can’t send or receive cellular, WiFi, Bluetooth, GPS, or NFC signals. It’s as if the phone doesn’t exist on any network.
How they work
Faraday bags use the same principle as a Faraday cage: a conductive mesh that distributes electromagnetic energy around the exterior, preventing it from reaching the interior. Your phone inside the bag:
- Can’t connect to cell towers (no calls, texts, or data)
- Can’t communicate via WiFi or Bluetooth
- Can’t receive GPS signals (no location tracking)
- Can’t transmit NFC
- Can’t be reached by cell-site simulators
When to use one
Preventing location tracking: Your phone continuously reports to cell towers. A Faraday bag stops this, creating a gap in your location history.
Sensitive meetings: Preventing audio eavesdropping via remotely activated microphones. Intelligence agencies and some stalkerware can activate your phone’s microphone. A Faraday bag prevents data exfiltration.
Device searches at borders: While you can’t prevent CBP from searching your device, a Faraday bag prevents remote wipe commands from reaching your phone while it’s being examined.
Counter-surveillance sweeps: TSCM professionals use Faraday bags to isolate devices during investigations.
Limitations
Not a substitute for powering off: Some phones perform limited operations even when “off.” A Faraday bag provides additional assurance.
Timing gaps reveal information: If your phone disappears from the network at the same time and place every week, that pattern itself is information.
Can’t receive communications: You’ll miss calls, messages, and notifications while the phone is in the bag.
Quality varies: Not all Faraday bags are equal. Cheap bags may not fully attenuate all frequencies. Test with your specific phone by placing it in the bag and calling it. If it rings, the bag doesn’t work.
Physical inspection still possible: A Faraday bag blocks wireless signals. If someone has physical access to your phone (outside the bag), all data is accessible.
Buying advice
- Test any Faraday bag before relying on it (call the phone while it’s inside)
- Look for bags that attenuate at least 60dB across cellular, WiFi, and Bluetooth frequencies
- Consider bags with dual-layer construction for reliability
- Don’t use a Faraday bag as your only privacy measure
Faraday bags address the network surveillance layer. They don’t address cameras (use Sentinel), web tracking (use Shield), or device-level compromise.