If it's technically possible at all then it's 100% true.
http://www.foreignpolicy.com/articles/2013/06/10/inside_the_...
"According to former NSA officials interviewed for this article, TAO's mission is simple. It collects intelligence information on foreign targets by surreptitiously hacking into their computers and telecommunications systems, cracking passwords, compromising the computer security systems protecting the targeted computer, stealing the data stored on computer hard drives, and then copying all the messages and data traffic passing within the targeted email and text-messaging systems. The technical term of art used by NSA to describe these operations is computer network exploitation (CNE).
TAO is also responsible for developing the information that would allow the United States to destroy or damage foreign computer and telecommunications systems with a cyberattack if so directed by the president. The organization responsible for conducting such a cyberattack is U.S. Cyber Command (Cybercom), whose headquarters is located at Fort Meade and whose chief is the director of the NSA, Gen. Keith Alexander."
You've seen Stuxnet and Flame which proves that they have zero-days and the code to access even networks not connected to the internet.
At least 3 submarines (including the USS Jimmy Carter) have the capability to tap into communications cables in the ocean which we've been doing it for at least 40 years.
http://en.wikipedia.org/wiki/National_Underwater_Reconnaissa...
http://www2.gwu.edu/~nsarchiv/nukevault/ebb305/index.htm
http://en.wikipedia.org/wiki/Project_Azorian
http://en.wikipedia.org/wiki/Operation_Ivy_Bells
Also more relating to the original article:
http://www.nti.org/
http://www.wilsoncenter.org/program/NPIHP
http://www2.gwu.edu/~nsarchiv/nukevault/index.htm