“Government spies 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, 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.”
http://www.nytimes.com/2013/11/26/technology/a-peephole-for-the-nsa.html?_r=0&pagewanted=all