Faraday Phone Pouch

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The electromagnetic spectrum

The electromagnetic spectrum or electric radio spectrum is not something material, but the space that is in the air that goes from the ground to the highest part of the sky. In this space, bands frequencies through which airplanes, wi-fi, bluetooth, walkie talkies, radios, telephones communicate are organized. The fact that our phones can be 2G, 3G, 4G means that they are using different bands of the electromagnetic space, through which the information circulates.

For more information about the electromagnetic space: https://imagine.gsfc.nasa.gov/science/toolbox/emspectrum1.html https://en.wikipedia.org/wiki/Electromagnetic_spectrum

Faraday Cage


It is known as a cage or box of Faraday the effect by which the electromagnetic field inside a conductor in equilibrium is null, nullifying the effect of the external fields. This is because, when the conductor is subjected to an external electromagnetic field, it is polarized, so that it is positively charged in the direction of the electromagnetic field, and negatively charged in the opposite direction. Since the conductor has been polarized, it generates an electric field equal in magnitude but opposite in the direction of the electromagnetic field, then the sum of both fields inside the conductor will be equal to 0.

It is evident in many everyday situations, for example, the malfunction of mobile phones inside elevators or buildings with steel grid structure. One way to check this is with a radio tuned to a Middle Wave station. When it is surrounded with a newspaper, the sound is heard correctly, but if we replace the paper with aluminum foil, the radio will cease to emit sounds: aluminum is an electric conductor and causes Faraday's cage effect.

This phenomenon, discovered by Michael Faraday in 1836, has an important application in airplanes or in the protection of sensitive electronic equipment, such as hard disks or radio and television repeaters located on mountain peaks and exposed to electromagnetic disturbances caused by storms . It also currently serves to block the reading of RFID (Radio Frequency Identifiers) chips, which store personal information that can be intercepted by anyone with a radio-frequency scanner. These chips are found in objects such as passports, credit cards and some driver's licenses.

The Faraday box allows to block the communication of a device with the outside. In the case of mobile phones, they emit signals constantly, even when they are switched off. GPS, which allows us to locate where we are, no matter if it is off or on, also the phone will be locateable by towers that triangulate the signals. The fact that your phone has no signal (when you can not call), does not imply that you are not locateable, or that you have stopped sending signals.

Some household appliances work as Faraday boxes, for example the freezer in the refrigerator, as having a thick layer of metal can have the same effect, if we introduce the cell phone inside, we prevent signals from being emitted.

About Faraday cage: https://en.wikipedia.org/wiki/Faraday_cage

Experiment of creating a Farady cage: https://backyardbrains.com/experiments/faraday

How they can intercept the information on your phone

One way to intercept the information on your phone is through an IMSI-catcher, a device that can be installed anywhere (a car, a house nearby, etc.), and which simulates to be the antenna of a telephone operator mobile. When installed, the cell phones of this operator will automatically connect with this fake antenna. Thus, this device locates and identifies the switched phones that are in the sector, even if they are not communicating, registering and sending information that identifies them (such as telephone number and device number).

The IMSI-catcher can also relay the communications out of a particular cell phone in such a way that it can not perceive its presence. This way you can have direct access to the content of these broadcast communications that relays and can serve as a live listening device.

You can read a HowTo on IMSI-catcher: https://gendersec.tacticaltech.org/wiki/index.php/Detect_false_mobile_antennas

Build a Faraday Pouch


There are several ways to make a bag for our mobile devices or tablets so that they are not traceable and do not emit signals through which we can be identified or spied upon.

You have to get the conductive textile first which can be bought online in places like these:

exemple 1

The most important thing is that when you make the cover there is no open space where the signal can leak. Make sure you sew all the edges, you can fold the textile before sewing it.

graphs from killyourphone.com

The sheath can be made with a sewing machine or by hand. You can design a way to close it, with a button, with velcro, or simply with a clamp.

If the textile is not very thick or powerful, you can use it twice. You can also, if you want to increase the aesthetics of your pouch, use another textile for the outer coating. You can try different designs and shapes, as shown in the drawing:

graphs from killyourphone.com

Additional safety measures for your pouch

Using in group the pouch can be a very suspicious technique if, for example, several monitored mobiles, located in the same area, are switched off or no longer connected to the network at the same time. If it is done this way it will make it evident that these people have something to hide or they are into something weird. In that sense, the safest practice is still to leave your phone in the house, or at least, remove the battery or put it in the case before leaving your house to not reveal the meeting place.

Be very careful as the Faraday bag does not cancel the microphone. Although the phone is incommunicado with the outside, could have installed some tool that allows to record and then send said recording. Be sure to keep the phone in an acoustically isolated location. You can put the phone with its case inside an airtight glass jar, in the refrigerator, or in another room.

Links de interés






Tests a jaulas y fundas de Faraday (foros):

http://www.survivalistboards.com/showthread.php?t=156111 http://www.survivalistboards.com/showthread.php?t=231373 http://www.survivalistboards.com/showthread.php?t=301999