What Is TEMPEST? Can Your Computer Be Eavesdropped From Outside?
Screens, keyboards and cables emit signals unintentionally. What TEMPEST protection is and which organizations need it.
3 min readSeptember 30, 2026
What Airplane Mode Does and Doesn't Do
Airplane mode switches off the phone's cellular radio through software. But it's a command, and it means trusting the phone's operating system. On some devices Wi-Fi and Bluetooth can be turned on in airplane mode or re-enable automatically.
More importantly, switching a phone to airplane mode requires unlocking the screen and interacting with the device. That leaves traces on the device and is recorded as an intervention the defense may challenge during the examination.
The Real Risk: Remote Commands
Modern phones can receive remote wipe, lock or location commands from their owner. If the device connects to a network even for a moment, such a command can run and the evidence is gone before the examination starts. Newer models that support satellite messaging increase this risk further.
That's why the basic rule in digital forensics is that the device must receive no wireless signal from seizure until the examination ends. The rule must rely on physics, not software.
Physical Isolation: Box, Bag and Room
In the field, the first step is placing the device in a shielded evidence box or Faraday bag. But bags wear out over time, and you can't work on a device inside one. Once at the lab, the examination needs an environment where the device can stay on and charging.
That environment is a cyber security room. Inside, there's no mobile network, Wi-Fi, Bluetooth or GPS signal; the examiner can work comfortably for hours while the device can't connect to the outside world.
The Right Workflow
In the field the device goes into a shielded box, at the lab it moves into the shielded room, and the whole examination happens there. There must be no moment in between when the device could receive a signal, which is why a double-door entry vestibule is recommended.
For field units, a shielded container provides the same protection away from headquarters. That way evidence reaches the court exactly as it was seized.
Frequently Asked Questions
Isn't switching the phone off enough?
It reduces some risks, but when restarted, encryption keys and some data may become inaccessible. Most examinations require the device to stay on.
How reliable is a Faraday bag?
It works for short-term transport, but an improperly closed flap or wear reduces performance. Long examinations need a shielded room.
Is satellite connectivity blocked too?
Yes. A properly designed cyber security room also blocks satellite frequencies; this is verified by measurement at handover.
Related Solutions
Let's Find the Right Solution for Your Project
Get a QuoteYour free site survey and quote will be ready within 24 hours.