When HN users recommended it
1 HN user recommended this in 2016, in one comment.
20072026
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FawkesBOX Smart phone Faraday Cage
Amazon's catalog no longer lists this product (checked 2026-11-02). The name comes from the link HN users posted.
The point is that there is such complexity in your average smartphone, that strictly enforcing radio silence with software from within is practically impossible.
Let's forget everything aside from GSM for a moment.
The GSM/LTE/whatever radio runs very closed source firmware. This communicates with the very closed source CPU and other subsystems, controlled by the very closed source OS. On top of that you run various other closed source apps, opening potentially malicious documents and browsing potentially malicious links.
In theory nothing goes wrong. When you hit 'airplane mode', the OS tells the radios to STFU. In practice, anything could go wrong - maliciously or not. Your phone could have been "jailbroken" without your knowledge by a 0-day exploit, effectively negating the OS security. Once the bad guys are in your OS, they may as well update your baseband firmware to do whatever they want. Or any of the other firmware/drivers/ICs that they are able to access. Or CPU microcodes. Anything.
Ideally you would have a phone with a physical switch, powering off all radios. Not politely instructing them to please cease functioning, but actually power them the f... off. This almost never happens. I have a hardware switch on my laptop - this doesn't actually cut the power to the wireless radios. If/when the firmware is compromised, it is as useless as the Wifi LED indicators.
So, great, you'll say - implement that rather than build a whole new system to babysit your smartphone stack. Make a hardware switch that powers off all radio subsystems. Even if that were possible, your iPhone would not like a subsystem disappearing from existence. It isn't designed to handle that contingency and will surely fail in spectacular ways.
Hence, tapping into debug ports/buses/etc and trying to monitor traffic that way.
The analog way[1] may make more sense, but usability would probably be restricted. I'm fairly certain Snowden has heard of faraday cages.
[1] https://www.amazon.com/FawkesBOX-Smart-phone-Faraday-Cage/dp...