The classified files, revealed today by the Danish newspaper Dagbladet Information in a reporting collaboration with The Intercept, shed light on how the NSA's surveillance of global communications has expanded under a clandestine program, known as RAMPART-A, that depends on the participation of a growing network of intelligence agencies.

It has already been widely reported that the NSA works closely with eavesdropping agencies in the United Kingdom, Canada, New Zealand, and Australia as part of the so-called Five Eyes surveillance alliance. But the latest Snowden documents show that a number of other countries, described by the NSA as "third-party partners," are playing an increasingly important role – by secretly allowing the NSA to install surveillance equipment on their fiber-optic cables.