The NSA has been found to tap into Level3’s backbone internet cables, through a variety of means.  According to Level3 financials, it seems they have an open agreement with the US departments of defense, justice, and homeland security.  More disturbing is the fact that if tech companies don’t cooperate, they’ll just get the data downstream (without anyone’s permission).  The irony, Google and Yahoo invest heavily in data center security, both electronic and physical.  But the weak spot is where data comes in and out of the centers, through miles of fiber optic cables.  From NY Times:

SAN FRANCISCO — The recent revelation that the National Security Agency was able to eavesdrop on the communications of Google and Yahoo users without breaking into either company’s data centers sounded like something pulled from a Robert Ludlum spy thriller.

How on earth, the companies asked, did the N.S.A. get their data without their knowing about it?

The most likely answer is a modern spin on a century-old eavesdropping tradition.

People knowledgeable about Google and Yahoo’s infrastructure say they believe that government spies bypassed the big Internet companies and hit them at a weak spot — the fiber-optic cables that connect data centers around the world and are owned by companies like Verizon Communications, the BT Group, the Vodafone Group and Level 3 Communications. In particular, fingers have been pointed at Level 3, the world’s largest so-called Internet backbone provider, whose cables are used by Google and Yahoo.

The Internet companies’ data centers are locked down with full-time security and state-of-the-art surveillance, including heat sensors and iris scanners. But between the data centers — on Level 3’s fiber-optic cables that connected those massive computer farms — information was unencrypted and an easier target for government intercept efforts, according to three people with knowledge of Google’s and Yahoo’s systems who spoke on the condition of anonymity.

It is impossible to say for certain how the N.S.A. managed to get Google and Yahoo’s data without the companies’ knowledge. But both companies, in response to concerns over those vulnerabilities, recently said they were now encrypting data that runs on the cables between their data centers. Microsoft is considering a similar move.

“Everyone was so focused on the N.S.A. secretly getting access to the front door that there was an assumption they weren’t going behind the companies’ backs and tapping data through the back door, too,” said Kevin Werbach, an associate professor at the Wharton School.

Data transmission lines have a long history of being tapped.

Also, in a financial filing, Level 3 noted that, “We are party to an agreement with the U.S. Departments of Homeland Security, Justice and Defense addressing the U.S. government’s national security and law enforcement concerns. This agreement imposes significant requirements on us related to information storage and management; traffic management; physical, logical and network security arrangements; personnel screening and training; and other matters.”

Security experts say that regardless of whether Level 3’s participation is voluntary or not, recent N.S.A. disclosures make clear that even when Internet giants like Google and Yahoo do not hand over data, the N.S.A. and its intelligence partners can simply gather their data downstream.

That much was true last summer when United States authorities first began tracking Mr. Snowden’s movements after he left Hawaii for Hong Kong with thousands of classified documents. In May, authorities contacted Ladar Levison, who ran Lavabit, Mr. Snowden’s email provider, to install a tap on Mr. Snowden’s email account. When Mr. Levison did not move quickly enough to facilitate the tap on Lavabit’s network, the Federal Bureau of Investigation did so without him.

Mr. Levison said it was unclear how that tap was installed, whether through Level 3, which sold bandwidth to Lavabit, or at the Dallas facility where his servers and networking equipment are stored. When Mr. Levison asked the facility’s manager about the tap, he was told the manager could not speak with him. A spokesman for TierPoint, which owns the Dallas facility, did not return a call seeking a comment.

Mr. Pitts said that while working as the chief legal officer at Nokia in the 1990s, he successfully fended off an effort by intelligence agencies to get backdoor access into Nokia’s computer networking equipment.

Nearly 20 years later, Verizon has said that it and other carriers are forced to comply with government requests in every country in which they operate, and are limited in what they can say about their arrangements.

“At the end of the day, if the Justice Department shows up at your door, you have to comply,” Lowell C. McAdam, Verizon’s chief executive, said in an interview in September. “We have gag orders on what we can say and can’t defend ourselves, but we were told they do this with every carrier.”