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Here Is the Contract for the UK's First Confirmed IMSI Catcher

A Scottish prison used the device to catch inmates using mobile phones.
Image: Shutterstock

In May, the Scottish Prison Service (SPS) became the first UK agency to admit that it had used IMSI catchers, in this case for blocking prisoners' phone calls.

Now, Motherboard has obtained the contract between the SPS and the device vendor. This is the first time that a contract for an IMSI catcher used in the UK has been published, providing more evidence that such devices are being deployed in the country, despite the government's lack of transparency on the matter.


"For years we've had indirect reports suggesting law enforcement use of this technology," said Matthew Rice, advocacy officer from Privacy International, in an email. "And now this, the first public contract for an IMSI Catcher in the UK we've ever seen. The technology has become a part of our institutions' surveillance arsenal without a proper discussion even taking place."

An SPS spokesperson confirmed to Motherboard that the IMSI catcher is still in operation at the site

IMSI catchers, sometimes referred to as Stingrays after a particularly popular brand of device, work by mimicking cell phone towers. The typically suitcase-sized devices force phones in their proximity to connect en masse, and then extract their IMSI number—a unique identifier given to each SIM card. This can then be used to track or attempt to identify the user.

Some IMSI catcher models are capable of intercepting calls and messages. The SPS uses the devices to block GSM, 2G, and 3G signals, as it is a criminal offence for prisoners to possess a mobile phone or other portable communications device.

Read More: In a First, UK Authority Admits to Using IMSI Catchers for Surveillance

Investigative journalism platform The Ferret previously reported that the SPS spent a total of £1.2 million ($1.6 million) on a pilot project demoing IMSI catchers at two different prisons throughout 2013 and 2014.

The partly redacted contract obtained by Motherboard via the Freedom of Information Act relates to one of those prisons: HMP Shotts. An SPS spokesperson confirmed to Motherboard that the IMSI catcher is still in operation at the site.


"The Scottish Prison Service gathers evidence to aid the detection of any crime that may have been committed. Going forward, we are taking forward regulations to allow the disconnection of mobile phones," the SPS spokesperson wrote in an email.

The 38-page contract is with Cobham TCS Limited, an established vendor of IMSI catchers and other surveillance tools. Much of the document covers standard legal issues, such as warranty and contract termination. Other sections lay out technical specifications of the device.

Image: screenshot from the contract

One part explains that Cobham must provide a training plan for SPS staff on how to use the technology. It adds that Cobham shall not be responsible for any injury, loss, damage, cost or expense caused by the negligence or willful misconduct of the SPS. This sort of clause is common in contracts throughout the surveillance industry.

Rice said the contract shows how little UK institutions may know about the scope of the technology they purchase.

"The requirements request no denial of access to the mobile networks for devices outside the perimeter fence," he said. "IMSI Catchers operate at distances up to 5km depending on the power configured and the protocol (2G, 3G) to be denied. This technology does not care about perimeter fences. It disrupts and overruns any mobile networks in its path. And at up to 5km, if not configured properly this could very well have affected the service for the nearby village, Dykehead."

Indeed, according to The Ferret, the SPS originally intended to trial the IMSI catcher at HMP Edinburgh, but concluded that the risk of accidentally blocking phone signals for people passing the prison was too high.

While the US has seen a lively debate around the use of IMSI catchers, the use of such devices in the UK is shrouded in secrecy.

"The time has come for the use of IMSI Catchers in the UK to become an open discussion," Rice added.