A faraday bag is a fabric or metal-mesh-lined enclosure that blocks radio-frequency signals from reaching the phone inside. Pioneered for forensic preservation (preventing remote wipe of seized devices in transit to the lab), now sold to consumers for privacy, security, and threat-protection use cases. Major brands: Mission Darkness, Silent Pocket, Faraday Defense, plus dozens of smaller producers.
What it means in practice
The bag’s effectiveness depends on the enclosure quality. A properly-shielded faraday bag blocks cellular, Wi-Fi, Bluetooth, GPS, and NFC signals; the device inside cannot transmit or receive. The threats this addresses: remote wipe of a phone you lost or had seized, surveillance of a phone’s ambient signals (cell-site triangulation, Bluetooth-beacon-network participation, Wi-Fi probe leakage), and live tracking via implant or stalkerware that depends on outbound network connectivity. The trade-off is that the phone is non-functional inside the bag; phone calls, text messages, and notifications all wait until the bag is opened.
Who uses it, and against whom
Operationally relevant for: travelers crossing hostile borders who want to power off and shield the device for the duration of the seizure window, journalists carrying sensitive devices through environments where ambient surveillance is realistic, activists in situations where real-time location is the targeting input, divorce clients during pre-filing investigation phases where the spouse may have access to Find My or stalkerware-driven location feeds, and forensic investigators carrying seized devices to the lab. Less relevant for: most everyday privacy use cases, where the operational discipline of “leave the phone home” or “power off and remove the SIM” addresses the same threats without buying a $50 to $150 bag.
What you can change today
If your threat model justifies a faraday bag, buy one from a reputable vendor (Mission Darkness or Silent Pocket are the established options; verify with a signal test before relying on it: phone goes in, attempt to call from another phone, the call should fail to connect). For travel: carry the device in the bag during transit, remove only at the destination on a network you trust. For meetings where ambient surveillance matters: phones in the bag for the duration. For day-to-day privacy: the structural answer remains “do not bring the phone to operations where it should not be present”; the bag is a complement to that discipline, not a replacement.