A Eurofighter Typhoon is seen in the middle of a laser show during the presentation and delivery of the 100th Eurofighter to the German airforce at headquarter of Military Air Systems Centre Cassidian in Manching near Ingolstadt, southern Germany, February 28, 2013. REUTERS/Michaela Rehle Edward Snowden, the 30-year-old whistleblower/leaker responsible for exposing U.S. government secrets, is now a fugitive.

The ex-Booz Allen employee revealed some of the covert practices of National Security Agency (NSA) — an organization "whose sole purpose is to listen to everyone in the world," according to "Deep State: Inside the Government Secrecy Industry" by journalists Marc Ambinder and D.B. Grady.

The book highlights why Snowden's revelations are so damaging to Uncle Sam's espionage operations:

"The most closely held secrets by the United States are what we know about everyone else's secrets and how we came to know them. The collection of communications between persons is called signals intelligence, or SIGINT, whether physically (communications intelligence, or COMINT) or electronically (ELINT)."

The NSA is the premier SIGINT enterprise in the world.

And Snowden, a former CIA technician-turned-NSA contractor, spilled "documents" about the NSA hacking China, the U.S. spying on its allies at diplomatic summits, the U.K. SIGNIT tapping Internet traffic and sharing it with the U.S., and a domestic dragnet that may be unconstitutional but continues to analyze the communications of Americans.

That's because Snowden knows a lot of what the NSA knows and, crucially, how the world's largest spy agency came to know it.

One thing that is still unknown is how much Snowden has leaked — e.g. What have Chinese and/or Russian intelligence authorities learned from him? — but it's clear that his actions have damaged America's ability to spy on everyone.