A story about the documents posted yesterday on the website The Intercept offered no details on how the intelligence agencies employed the eavesdropping capability, providing no evidence, for example, that they misused it to spy on people who weren't valid intelligence targets.
But the surreptitious operation against the world's largest manufacturer of mobile phone data chips is bound to stoke anger around the world.
The targeted company, Netherlands-based Gemalto, makes "subscriber identity modules," or SIM cards, used in mobile phones and credit cards. One of the company's three global headquarters is in Austin, Texas.
Its clients include AT&T, T-Mobile, Verizon and Sprint, The Intercept reported.
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The Intercept offered no evidence of any eavesdropping against American customers of those providers, and company officials told the website they had no idea their networks had been penetrated. Experts called it a major compromise of mobile phone security.
The NSA, like the CIA, breaks the espionage and hacking laws of other countries to get information that helps American interests.
Still, the methods in this case may prove controversial, as did earlier Snowden revelations that the NSA was hacking transmissions among Google's data centers.
The Intercept reported that British government hackers targeted Gemalto engineers around the world much as the US often accuses Chinese government hackers of targeting Western companies, stealing credentials that got the hackers into the company's networks.
That allows them to ungarble calls, texts or emails intercepted out of the air.