They seem to monitor all kinds of EM radiation. Maps.
1. What is Signals Intelligence?
SIGINT involves collecting foreign intelligence from communications and information systems and providing it to customers across the U.S. government, such as senior civilian and military officials. They then use the information to help protect our troops, support our allies, fight terrorism, combat international crime and narcotics, support diplomatic negotiations, and advance many other important national objectives.
NSA/CSS collects SIGINT from various sources, including foreign communications, radar and other electronic systems. This information is frequently in foreign languages and dialects, is protected by codes and other security measures, and involves complex technical characteristics. NSA/CSS needs to collect and understand the information, interpret it, and get it to our customers in time for them to take action. Our workforce is deeply skilled in a wide range of highly technical fields that allow them to this work, and they develop and employ state-of-the-art tools and systems that are essential to success in today's fast-changing communications and information environment. Our researchers are working constantly to help us anticipate and prepare for future developments.
Some internet connectivity maps are here - http://www3.nd.edu/~...y/gallery_old.htm
China tries to monitor everything on their network. They don't succeed. http://www.theatlant...een-reset/306650/
My $0.02.
Cheers,
Scott.