British and US intelligence agencies are now facing accusations of hacking into a major manufacturer of mobile phone Sim cards, in a bid to steal codes and facilitate eavesdropping, reports a US news website.
Could your Sim have been hacked?
The Intercept site says that Edward Snowden gave them the information - a former American intelligence contractor who is currently living in Russia.
Gemalto, the company which was allegedly targeted and operates in 85 countries is now said to be taking these allegations "very seriously".
Being labelled as "the great Sim heist", the Intercept website says that it gave US and British surveillance agencies "potential to secretly monitor a large portion of the world's cellular communications, including both voice and data".
It goes on to say that amongst the clients of the company are "some 450 wireless network providers around the world", including Verizon, Sprint, T-Mobile and AT&T.
Britain's GCHQ and American's National Security Agency are said to be the organisations who used the hack in 2010, and both agencies have yet to comment.
Data would be able to be decoded between cell towers and mobile phones, meaning the hackers were able to un-garble intercepted calls, emails and texts from out of the air.
Reuters news agency was told by a Gemalto spokeswoman that whilst their company wasn't targeted "per se", there was "an attempt to try and cast the widest net possible to reach as many mobile phones as possible".
"We take this publication very seriously and will devote all resources necessary to fully investigate and understand the scope of such highly sophisticated techniques to try to obtain Sim card data," she said.
Gemalto furnishes service providers with encryption codes in a bid to keep data on each phone private.
The Intercept says that by cyber-stalking Gemalto employees and penetrating their emails, the agencies were able to steal at source thousands of those codes.
Correspondants state that these fresh revelations are highly embarrassing for the agencies involved, as it gives an impression of them doing anything it takes to improve their surveillance powers, even if that means having to steal data from law-abiding Western firms.