conejota - Fotolia

Prison services worked with Ofcom in test of mobile phone blockers

Documents reveal trials of mobile traffic interception technology in UK jails, which may have affected users beyond the prison walls

The Scottish Prison Service (SPS) and the National Offender Management Service (NOMS) collaborated with EE, O2, Three and Vodafone in the use of mobile phone blocking technology that may have affected legitimate network users outside the walls of prisons.

Illicit mobile phone use is a serious concern in UK prisons as they can be used for a number of criminal purposes, including drug dealing, commissioning of criminal activity outside of prison and involvement in organised crime or terrorism.

The SPS and NOMs have long tried to disrupt this by seeking to stop mobile devices from entering their sites in the first place, but has now turned to mobile phone signal detection and denial equipment – known as international mobile subscriber identity (IMSI) catchers – to stop inmates from carrying on criminal activity.

IMSI catchers, which are also generically known as StingRays, have also been used in the US to simulate mobile phone masts, essentially fooling a device into connecting to them so they can be tracked. These are subject to oversight by the US Department of Justice, and a warrant is required to operate one.

However, a cache of documents obtained by investigative website The Ferret have confirmed that IMSI trackers have been used in the UK, and may have negatively affected users that they were not meant to.

IMSI trials

A series of heavily redacted emails, between Ofcom’s Mobile and Wireless Broadband Spectrum Policy Group and the SPS operations directorate in Edinburgh, has revealed the existence of a trial of the technology, which began at HMP Shotts in Lanarkshire in April 2014. Notice of the test was delivered to Ofcom, which oversaw the trial in an advisory capacity, on 20 February 2016.

The email to Ofcom, from an undisclosed address, said it was “our intention” to deploy IMSI catchers in these sites “for the foreseeable future” and “at least the next financial year”. The email sought Ofcom’s opinion on whether or not the SPS would need to notify Ofcom on a quarterly basis of the equipment deployed.

A second trial is known to have occurred at HMP Glenochil in Alloa.

IMSI defeated

The cache of documents also included a letter from the SPS to Ofcom dated 22 March 2016, purporting to be an annual statement on the use of an IMSI catcher at Shotts. The existence of the tracker was also confirmed following a Freedom of Information request earlier in 2016.

The SPS claimed the tracker collected only a device’s international mobile station equipment identity (IMEI) and IMSI numbers, along with a date and time stamp.

However, the SPS also reported that prisoners had developed “innovative” ways of getting around the IMSI catchers. According to the Ferret, this resulted in an increase in the number of illicit devices in circulation.

Additionally, it appears that the IMSI catchers could stop only 2G and 3G network traffic, rendering them ineffective against 4G-enabled smartphone devices, something else the prisoners soon figured out.

Harmful interference

A further document, again obtained by The Ferret, detailed a memorandum of understanding (MoU) between the SPS, Ofcom, and all four of the UK’s mobile network operators, EE, O2, Three and Vodafone.

A second MoU between Ofcom, the MNOs and the NOMS in England and Wales was practically identical, and covered potentially “all prisons, young offender institutions and secure training centres”.

The documents said the presence of illicit mobiles in prisons presented serious risk to their security and that of the public.

They went on to set out what equipment was being deployed – fixed or portable signal denial equipment – and established a framework by which Ofcom would advise both the SPS and NOMS on technical, co-ordination and interference, while acting as a mediator between the services and the MNOs. This was done “to ensure that appropriate procedures are put in place and followed, in the event of interference arising beyond the prison perimeter that may be attributable to the use of the equipment”.

Read more about Ofcom

Importantly, both documents set out the following: “The equipment has the potential to cause harmful interference to the operators’ customers who are legitimately using their mobile devices in the vicinity of prisons and/or the network equipment of the operators.

“Not only could this be extremely inconvenient to operators’ customers, disrupting their personal and business activities, but interference could also put people at risk by preventing access to services such as 999 emergency services from affected mobile phones.”

The documents also said that if public confidence in the use of IMSI catchers and access to 999 services was to be maintained, it was essential that complaints were met with a quick response, and set out a number of steps that would have to be taken in those circumstances.

Names of the signatories to the NOMs document were redacted, but the SPS document was signed on 10 February 2014 by SPS chief executive Colin McConnell. Representatives of EE, Hutchison 3G, Telefónica and Vodafone also signed the document. None of these names were revealed in the documents.

However, in January 2016, a spokesperson for O2 told Vice News it had “no agreements” with the government or any security agencies concerning the use of IMSI catchers.

Vice’s investigation suggested that IMSI catchers had also been deployed around the Houses of Parliament, at the Ecuadorian embassy where Wikileaks’ Julian Assange continues to base himself and alongside anti-austerity protest marches.

Ofcom said that it was right and proper that the regulator took part in such trials in order to minimise risk to ordinary consumers, and backed the view of the prison services that mobile access within UK jails needed to be severely restricted.

A spokesperson said: "The blocking of mobile phones in prisons is a matter for the government. However, as the spectrum regulator, Ofcom has an important role to protect consumers from any harmful interference. So we have rightly been working with operators and the government to minimise the risk of effects outside prisons.”

Read more on Mobile networking