NSA snooping confounds experts at Google, Yahoo

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 centres has confounded experts at the companies.

How could their data have been compromised without their getting wind of it?

The agency could have deployed a century-old method giving it a modern twist.

According to people in the know about Google and Yahoo's infrastructure, it was likely that government agencies bypassed the big internet companies and targeted a weak spot - the fibre-optic cables connecting data centres around the world, owned by companies like Verizon Communications, the BT Group, the Vodafone Group and Level 3 Communications.

The needle of suspicion pointed at Level 3, the world's largest so-called internet backbone provider, whose cables were used by Google and Yahoo.

The internet companies' data centres were locked down with full-time security and state-of-the-art surveillance, which included heat sensors and iris scanners.

However, between the data centres - on Level 3's fibre-optic cables connecting the massive computer farms - information was unencrypted and an easier target for government intercept efforts experts opine.