Police use 'fake mobile masts' to listen in to people's calls without their knowledge

National Crime Agency's director general says 'some of what we need to do is intrusive; it is uncomfortable'

Mobile phone mast lookalikes are being used by police agencies to listen in on people's calls without their knowledge in a bid to track down criminals.

In an investigation, Sky News found that IMSI catchers, also known as Stingrays, were being used in the UK to collect data from phones within a certain radius of their location, meaning that innocent people were being spied on without realising.

Eric King, deputy director of Privacy International suggested that IMSI catchers were hard to use in a targeted way.

"In an urban space, thousands of people's mobile phones would be swept up in that dragnet. What they do with that data, we don't know," he told Sky News.

He added that it was known that police agencies worldwide had used this technology in the past, but this was the first evidence of any being deployed in the UK.

German security company GMSK Cryptophone's software was used to find evidence of Stingray activity, and the investigation's complete data logs have been published online.

But despite this evidence, and several Freedom of Information (FOI) requests made by Sky News to the Metropolitan Police, the organisation refused to confirm or deny its use of IMSI catchers.

Bernard Hogan-Howe, the Met commissioner, suggested it was only criminals who would benefit from knowing exactly what the police agency uses as a means to catch criminal activity.

He also emphasised that those people who are worried about their privacy should be reassured that it would be impossible to carry out as much intrusion as is often thought because it does not have the resources to do so.

The National Crime Agency (NCA) was also coy when asked by Sky News about IMSI use by police agencies, again suggesting that revealing details would only benefit criminals.

Keith Bristow, director general of the NCA said: "Frankly, some of what we need to do is intrusive; it is uncomfortable, and the important thing is we set that out openly and recognise there are difficult choices to be made."

The reactions of the Met Police and National Crime Agency should not come as a surprise as these are typical responses from government agencies on their continued use of surveillance techniques which were first brought to mainstream attention by former US government security contractor Edward Snowden.