The controversy over National Security Agency (NSA) spying has continued with an article from The Washington Post that accused the agency of secretly monitoring transmissions between the data centres of Internet giants Yahoo and Google.
In a statement, both firms denied cooperating with such a scheme, with Google saying it was "outraged" by the revelation.
The effort, internally referred to as MUSCULAR, operates in conjunction with the UK's Government Communications Headquarters (GCHQ).
"From undisclosed interception points, the NSA and GCHQ are copying entire data flows across fiber-optic cables that carry information between the data centers of the Silicon Valley giants," according to the Post.
The information came from documents leaked by former NSA contractor Edward Snowden. As the Post noted, the news is startling because, despite the wealth of tech tools at its disposal, the NSA "has not been known to use them routinely against U.S. companies."
In a statement, the NSA said it has "multiple authorities that it uses to accomplish its mission, which is centered on defending the nation."
"The Washington Post's assertion that we use Executive Order 12333 collection to get around the limitations imposed by the Foreign Intelligence Surveillance Act and FAA 702 is not true," the agency continued.
"The assertion that we collect vast quantities of U.S. persons' data from this type of collection is also not true. NSA applies Attorney General-approved processes to protect the privacy of U.S. persons – minimizing the likelihood of their information in our targeting, collection, processing, exploitation, retention, and dissemination. NSA is a foreign intelligence agency. And we're focused on discovering and developing intelligence about valid foreign intelligence targets only."
"We have long been concerned about the possibility of this kind of snooping, which is why we have continued to extend encryption across more and more Google services and links, especially the links in the slide," David Drummond, Google's chief legal officer, said in a statement. "We do not provide any government, including the U.S. government, with access to our systems. We are outraged at the lengths to which the government seems to have gone to intercept data from our private fiber networks, and it underscores the need for urgent reform."
"We have strict controls in place to protect the security of our data centers, and we have not given access to our data centers to the NSA or to any other government agency," a Yahoo spokeswoman said.
MUSCULAR differs from PRISM, another scheme revealed by Snowden, which provides access to tech customers' metadata via secret court requests.
The news comes amidst reports that the NSA has been spying on prominent world leaders, including German chancellor Angela Merkel, which prompted talk of a walled-off Internet in Germany. According to Reuters, President Obama recently took steps to curb such surveillance, in particular at the United Nations.