How to isolate your mobile phone. Your mobile phone’s communications – texts, calls and emails – can be intercepted with relative ease if you become a target for skilled, unscrupulous operators. Another major risk is location tracking: your phone can reveal where you are, and when you were there. That is why some journalists keep a small pouch in their backpack. Put your smartphone inside it before you go to meet a sensitive source at a specific place, and the pouch can cut the device off from external signals. Your movements are no longer traceable through the phone. It is known as a “Faraday bag”, named after the British physicist Michael Faraday, born in 1791, who devised the idea of a cage shielded from electrostatic fields outside it. These signal-blocking pouches are generally inexpensive.