<p><b>The plague of killer texts</b></p><p>Warnings circulating in Egypt claimed that people suffered fatal brain haemorrhages after receiving a 'killer' mobile phone text message from 'unknown foreign quarters' containing a special combination of numbers

‘Stingray’ cell towers trick phones into thinking they’re connecting to a network, and let anyone listen in

The US Federal Bureau of Investigation has argued that it should be able to listen in on phone calls using technology that tricks phones into thinking they’re connecting to normal masts. The tools, called “Stingrays”, allow users to intercepts calls and texts.

While the FBI’s policy states that it should obtain a search warrant, it does not have to if the technology is used in a public place, according to a letter published by Chuck Grassley, a Republican senator for Iowa.

The letter is partly a response to increasing concern about the use of the technology in the US. The FBI is mounting the tools on small aeroplanes, according to a report by the Wall Street Journal.

While the technology is used to target criminals, it gives access to the phone calls of any innocent Americans that are in the area, according to the WSJ. Similar technology, called “dirtboxes” are capable of gathering data from tens of thousands of phones in one flight.

The letter also complains that little is known about the technology, how it works or to what degree the information gathered is shared.

The letter asks the US attorney general and secretary of homeland security a series of questions about the tools. It asks how often they are used and how.