Faraday bags, no matter how effective they are, can only block radio communications. Cell phones can do malicious things that don’t involve using radios.
Modern mobile phones have become highly complex, with a large amount of delicate electronic hardware controlled almost entirely by microprocessors and software. While this is good news for functionality, it is bad news for security. For devices such as smartphones, the software controls almost everything about the phone, including how and when to turn the power on and off. In other words, the phone “has its own ideas”, including understanding “shutdown”. signal jammer
The complex software systems of mobile phones are, to put it mildly, largely beyond the control of the user, especially in the case of smartphones equipped with microphones, cameras, location and environmental sensors, and communication links, and bugs in the software that controls them (or backdoors) and security vulnerabilities can have severe privacy implications.
It’s hard for people to reliably turn off software-based devices like smartphones completely, and this isn’t a persecuted fantasy, and some phone manufacturers even consider it a thoughtful feature. For example, some Apple iPhones continue to send Find My Device tracking beacons even when they are turned off. Even on devices that don’t “officially” support this feature, it’s possible for bad actors or malware to behave similarly, turning your phone into a permanent covert tracking device, regardless of whether you’ve turned it “off.” The risk of “false shutdown” is compounded by the non-removable batteries in many of the latest smartphones.
A well-known and popular method for those who want to ensure that their phone is isolated in certain scenarios and completely block the phone’s radio (including sending and receiving cell tower information, wifi, Bluetooth and NFC near-field communications, and GPS positioning signals) is to The phone was thrown into something called a “Faraday bag.”
The Faraday cage effect produced by Faraday bags can severely weaken or even block the radio signals of the devices inside, and is widely used to ensure that untrusted devices (such as mobile phones) can send and receive signals in unknowing or inappropriate scenarios. The principle of a Faraday cage is simple: it is just a solid conductive container that completely encloses the signal source, so that the RF voltage difference between any two points on the cage is always zero.
But in reality, building a Faraday cage system that works well in practice is not as simple as it seems. Any poorly sealed opening can create a junction that acts as an RF feed and significantly reduces attenuation efficiency.
Currently, some expensive (usually around a few hundred yuan) so-called commercial Faraday bags are hotly sold on e-commerce platforms. They are specially used for mobile phones and can be used to prevent commercial espionage or “pregnant women to protect themselves from radiation.” In addition, there are also a large number of claims on the Internet that claim to be able to temporarily shield The “local method” of mobile phone signal.
