The operation - dubbed MUSCULAR - was revealed in a document dated Jan. 9, 2013 and shared with the news outlet by NSA whistleblower Edward Snowden.
In it is explained that the GCHQ has directed all the information that passed through those cables to a "buffer", and that every three to five days the NSA would sift through it with custom-built NSA tools and collect data they considered important and helpful.
This data included metadata but also the contents of users accounts, including emails, stored images, search queries, and so on.
After having denied knowing anything about these activities, Google's chief legal officer David Drummond said that Google has long been concerned about the possibility of this kind of snooping, which is why they have continued to extend encryption across more and more Google services and links.
Last month's statement by Google that they began encrypting internal traffic a short time before the leaked NSA documents began hitting the news and that it continues with those efforts seems to confirm his statement, and so do internal Google sources that said that they suspected governments of attempting to tap their cables, but they never had any proof.
“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,” added Drummond.
The NSA is, as usual, trying to point out that they had valid authority to do this.
"NSA 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," they stated for the Post.
"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.”