Documents leaked by former United States National Security Agency (NSA) contractor Edward Snowden have revealed that spy agencies in the US and the United Kingdom hacked into the internal networks of the world's largest mobile SIM card manufacturer and stole encryption keys used to protect individuals' communications data.
The Intercept reported on Friday that top-secret documents provided to it by Snowden indicated that a joint unit comprised of operatives from the NSA and Britain's Government Communications Headquarters (GCHQ) had hacked into the internal systems of global Netherlands-headquartered SIM card manufacturer Gemalto.
Gemalto, which operates in 44 countries and counts 1.5 billion users of its products worldwide, develops and installs secure software and other related products such as SIM cards and credit card chips.
It is estimated that Gemalto produces up to 2 billion SIM cards per year, each of which is dispatched with an individual subscriber authentication key, or "Ki". Its SIM card clients include AT&T, T-Mobile, Verizon, Sprint, and around 450 wireless network providers globally.
The encryption keys were stolen following the breach of Gemalto's internal systems, revealed in a secret GCHQ document from 2010 published by The Intercept, would have given the intelligence agencies the potential to listen in on a significant proportion of the planet's voice and data mobile communications.
While most governments' intelligence and law-enforcement agencies are able to legally tap into communications content with a warrant, the possession of the encryption keys allow such agencies to listen in on communications without leaving a trace, effectively eliminating the necessity of a warrant or similar permission to obtain access to decrypted communications content.
According to The Intercept, Gemalto was unaware of the breach, with Paul Beverly, an executive vice president of the company, saying that he was "disturbed, quite concerned" that it had happened.
"Gemalto -- successfully implanted several machines and believe we have their entire network -- TDSD are working the data," a GCHQ document said.
Meanwhile, a 24-page report dated April 27, 2010, included in the leaked documents published by The Intercept, explores the introduction of an automated technique aimed at increasing the volume of keys that can be harvested by the agencies.
"TDSD has developed a methodology for intercepting these keys as they are transferred between various network operators and SIM card providers," the paper said, before outlining work that had gone into developing an automated system to extract keys.
"This work has demonstrated that an automated method of Ki recovery, once in place, can deliver significant results with little manual effort compared to current harvesting methods," the report said.
The documents revealing the agencies' breach of Gemalto's internal systems and the resulting SIM authentication key theft represents the latest revelation in an ever-growing list of discoveries revolving around the extent of digital spying carried out by intelligence agencies in the US, the UK, and other Five Eyes countries.
In January, documents leaked by Snowden revealed that the NSA is putting network attacks launched by other countries to its own use in a bid to gear up for digital war.
In July last year, a fresh set of the Snowden documents showed how the UK intelligence agency can manipulate online polls and debates, spread messages, snoop on YouTube, and track Facebook users.
In 2013, documents revealed the extent of the NSA's PRISM surveillance program, through which the US government collected internet communications of foreign nationals.