The National Security Agency has secretly broken into the main communications links that connect Yahoo and Google data centers around the world, according to documents obtained from former NSA contractor Edward Snowden and interviews with knowledgeable officials.
By tapping those links, the agency has positioned itself to collect at will from among hundreds of millions of user accounts, many of them belonging to Americans.
The NSA does not keep everything it collects, but it keeps a lot.
According to a top secret accounting dated Jan. 9, 2013, NSAs acquisitions directorate sends millions of records every day from Yahoo and Google internal networks to data warehouses at the agencys headquarters at Fort Meade, Md.
In the preceding 30 days, the report said, field collectors had processed and sent back 181,280,466 new records – including metadata, which would indicate who sent or received emails and when, as well as content such as text, audio and video.
The NSAs principal tool to exploit the data links is a project called Muscular, operated jointly with the agencys British counterpart, 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.
The infiltration is especially striking because the NSA, under a program known as Prism, has front-door access to Google and Yahoo user accounts through a court-approved process.
The Muscular project appears to be an unusually aggressive use of NSA tradecraft against flagship American companies.
The NSA is built for high-tech spying with a wide range of digital tools, but it has not been known to use them routinely against U.S. companies.
White House officials and the Office of the Director of National Intelligence, which oversees the NSA, declined to confirm, deny or explain why the agency infiltrates Google and Yahoo networks overseas.
In a statement, Google said it was troubled by allegations of the government intercepting traffic between our data centers, and we are not aware of this activity.
We have long been concerned about the possibility of this kind of snooping, which is why we continue to extend encryption across more and more Google services and links, the company said.
At Yahoo, a spokeswoman said: 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.
Under Prism, the NSA already gathers huge volumes of online communications records by legally compelling U.S. technology companies, including Yahoo and Google, to turn over any data matching court-approved search terms.
Intercepting communications overseas has clear advantages for the NSA, including looser restrictions and less oversight.
NSA documents about the effort refer directly to full take, bulk access and high volume operations on Yahoo and Google networks.
Such large-scale collection of Internet content would be illegal in the United States, but the operations take place overseas.
Outside U.S. territory, statutory restrictions on surveillance seldom apply, and the Foreign Intelligence Surveillance Court has no jurisdiction.
Senate Intelligence Committee Chairwoman Dianne Feinstein has acknowledged that Congress conducts little oversight of intelligence-gathering under the presidential authority of Executive Order 12333, which defines the basic powers and responsibilities of the intelligence agencies.
The operation to infiltrate data links exploits a fundamental weakness in systems architecture. To guard against data loss and system slowdowns, Google and Yahoo maintain fortresslike data centers across four continents and connect them with thousands of miles of fiber-optic cable.
These globe-spanning networks, representing billions of dollars of investment, are known as clouds because data moves seamlessly around them.
In order for the data centers to operate effectively, they synchronize high volumes of information about account holders. Yahoos internal network, for example, sometimes transmits entire email archives – years of messages and attachments – from one data center to another.
Tapping the Google and Yahoo clouds allows the NSA to intercept communications in real time and to take a retrospective look at target activity, according to one internal NSA document.
In order to obtain free access to data center traffic, the NSA had to circumvent gold standard security measures.
Google goes to great lengths to protect the data and intellectual property in these centers with tightly audited access controls, heat-sensitive cameras, round-the-clock guards and biometric verification of identities, according to one of the companys blog posts.
Google and Yahoo also pay for premium data links, designed to be faster, more reliable and more secure. In recent years, each is said to have bought or leased thousands of miles of fiber-optic cables for its exclusive use.
They had reason to think, insiders said, that their private, internal networks were safe from prying eyes.