I've been hunting for this for a long time. I've been able to find "Faraday" bags that (allegedly) block signals to/from the surveillance unit (phone), but they never mention anything about soundproofness, which is just as important IMO.

Let's say somebody puts their phone into one of those "Faraday bags" and they talk with their friend about private matters. While the phone cannot directly send this recorded audio back home, nothing stops it from doing it the very moment it again is able to send and receive signals.

Also, any built-in hardware would be able to record the movements of the phone the coordinates home, perhaps with just a little worse accuracy than if it had the cellphone towers' signals to compare to in real time.

I mostly worry about the audio being recorded, though, yet none of those bags even mention sound at all. It seems pointless to buy such a thing that just stops "direct"/realtime signals, but does nothing to prevent (slightly lagged) data leaks.

Is there a "cellphone securer" bag that I can buy, so that I can be around somebody who insists on having a phone with them at all times, so that they in theory could stop, take it out from the bag, and use it to make an emergency call or whatever?

  • 2
    Why shutting down is not an option? Aluminium pouch will block outside signals so your device will be in dormant state anyway.
    – defalt
    Aug 10 '21 at 15:57
  • If its in a faraday cage, how would it get location signals to record?
    – schroeder
    Aug 10 '21 at 16:06
  • A "bag" would be a poor thing to block sound. You'd need something hard. And turning off the phone would appear to solve all your problems.
    – schroeder
    Aug 10 '21 at 16:09
  • 1
    @defalt Because it's not possible to actually shut down a modern smartphone. Especially not now that batteries cannot even be removed at all.
    – L. H.
    Aug 10 '21 at 16:13
  • 1
    Consumer graded phones and laptops can be fully shutdown. You can verify it using thermal camera, SDR and infrasonic recorder.
    – defalt
    Aug 10 '21 at 16:29

A classic conundrum when dealing with forensics and mobile phones is how to handle them as evidence.

First of all Faraday shield pouches, or even shielded boxes, are not shields they are attenuators (presuming you don't have a superconducting shield).

Placing an active phone in a shield (attenuator) will cause the phone to ramp up it's power levels in an attempt to punch through. Depending upon the shield and ranges, the phone may succeed. Whether the phone succeeds in punching through or not, it will now rapidly burn through its battery charge.

Not shielding the phone leaves it vulnerable to remote access.

Generally phones seized for evidence are not shielded in order to preserve a better chance of accessing their content, but things change.

In high security locations, the general guide is to leave the phone physically outside and away from any possibility of the microphones or cameras picking up something.

So to directly answer your question: No there is no sound & signal blocker.

Best practice used to be, "Remove the Battery". With so many phones these days, that is no longer practical. Current practice is "Turn the Phone Off".

Where security concerns are high enough that turning the phone off is not trusted, the requirement is "Physical Separation".

  • Or, a box. This entire thing can be accomplished with a solid beach phone case in a signal "blocking" bag. So, no single solution but a simple combo. Recording abilities can easly be tested in the case.
    – schroeder
    Aug 10 '21 at 16:31
  • @schroeder - While there are many products marketed as "blocking", there really is no such thing. They are signal attenuators. Aug 10 '21 at 19:06
  • yes, I understand, that's why the quote marks.
    – schroeder
    Aug 10 '21 at 19:20

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