Mobile phone tapping in UK
Evidence found of rogue towers called Stingrays that listen in on people’s calls
Evidence has surfaced this week that operational rogue mobile phone towers, which can listen in on people's calls without their knowledge, are being operated in the UK.
IMSI catchers, also known as Stingrays, mimic mobile phone masts and trick phones into logging on.
The controversial surveillance technology is used by police agencies worldwide to target the communications of criminals.
However, Stingrays also collect the data of all other phones in the area, meaning innocent people's communications are spied on.
"With IMSI catchers, it's very difficult for them to be used in a targeted manner," Eric King, deputy director of Privacy International, said.
"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.
"We know police have been using them for years, but this is the first time that it's been shown that they're being deployed in the UK," Mr King said.
The discovery was made by Sky News who used software made by GMSK Cryptophone, a German security company, to look for the tell-tale signs of Stingray activity.
Over three weeks, Sky News discovered more than 20 instances in London. This is believed to be the first direct evidence of Stingray use in the UK.
The CEO of Cryptophone, Bjoern Rupp, said: "The discovery can clearly be categorised as strong indicators for the presence of IMSI catchers in multiple locations."
In November, The Times reported that the Metropolitan Police Service, the UK's largest police force, was using Stingray technology, citing anonymous sources.
And according to The Guardian, the Metropolitan Police paid £143,455 for the surveillance equipment in 2009.
Despite repeated Freedom of Information requests, the Met neither confirms nor denies that the force uses IMSI catchers.
Asked directly about the force's use of stingrays, Bernard Hogan-Howe, the Met commissioner and the UK's most senior police officer, said: "We're not going to talk about it, because the only people who benefit are the other side, and I see no reason in giving away that sort of thing.
The police's refusal to comment on IMSI catchers means the legal framework that governs their use is unclear and near impossible to say exactly who is operating the stingrays detected.
IMSI catchers are nowadays available to buy on the internet for around £1,000. This raises the possibility that they might be used by foreign governments, private enterprises, or criminals to steal UK citizens' personal data.