First Response & Preservation Technical Explainer
What is a Faraday bag and what can it do?¶
A Faraday bag is a shielded container designed to reduce radio-frequency communication between a device and surrounding wireless networks.
It can be useful for wireless containment, but it is not a magic evidence-preservation box.
The short version
A Faraday bag can reduce wireless communication while the device remains powered and active inside.
What it is trying to block¶
Depending on the equipment and frequency performance, shielding may reduce communication over routes such as:
- mobile networks;
- Wi-Fi;
- Bluetooth; and
- other radio systems.
OutsideWireless networks and nearby devicesSignals exist around the exhibit.
ShieldFaraday bagDesigned to attenuate radio communication.
InsideDevice remains poweredApps, timers and storage can continue changing.
Record the device before sealing it¶
Capture, where visible:
- screen;
- power state;
- battery;
- connections;
- applications;
- notifications; and
- visible time.
Once sealed, you may not be able to observe the screen.
Record the containment method too¶
Note:
- bag identity;
- visible condition;
- seal;
- placement time;
- operator; and
- verification method used under local procedure.
Performance depends on the equipment, frequencies, wear and correct sealing.
What are the limitations of a Faraday bag? covers those risks.
The device keeps running¶
Inside the bag:
- battery continues to drain;
- applications continue;
- local logs may change;
- previously received commands may still execute; and
- a cable can create another route.
The practical point is: use a Faraday bag as a documented wireless-control method, and plan for battery, handling and later examination from the start.
