One Ring to rule them all, One Ring to find them, One Ring to bring them all and in the darkness bind them

wsj | The NSA is focused on collecting foreign intelligence, but the streams of data it monitors include both foreign and domestic communications. Inevitably, officials say, some U.S. Internet communications are scanned and intercepted, including both "metadata" about communications, such as the "to" and "from" lines in an email, and the contents of the communications themselves.

Much, but not all, of the data is discarded, meaning some communications between Americans are stored in the NSA's databases, officials say. Some lawmakers and civil libertarians say that, given the volumes of data NSA is examining, privacy protections are insufficient.

Sen. Ron Wyden, an Oregon Democrat, in 2012 sought but failed to prohibit the agency from searching its databases for information on Americans without a warrant. He has also pushed intelligence agencies to detail how many Americans' communications have been collected and to explain whether purely domestic communications are retained in NSA's databanks. They have declined.

"Technology is moving us swiftly into a world where the only barriers to this kind of dragnet surveillance are the protections enshrined into law," Mr. Wyden says.

This month President Barack Obama proposed changes to NSA surveillance to improve oversight. Those proposed changes wouldn't alter the systems in the U.S. that NSA relies upon for some of its most sensitive surveillance.

The systems operate like this: The NSA asks telecom companies to send it various streams of Internet traffic it believes most likely to contain foreign intelligence. This is the first cut of the data.

These requests don't ask for all Internet traffic. Rather, they focus on certain areas of interest, according to a person familiar with the legal process. "It's still a large amount of data, but not everything in the world," this person says.

The second cut is done by NSA. It briefly copies the traffic and decides which communications to keep based on what it calls "strong selectors"—say, an email address, or a large block of computer addresses that correspond to an organization it is interested in. In making these decisions, the NSA can look at content of communications as well as information about who is sending the data.

One U.S. official says the agency doesn't itself "access" all the traffic within the surveillance system. The agency defines access as "things we actually touch," this person says, pointing out that the telecom companies do the first stage of filtering. 

The surveillance system is built on relationships with telecommunications carriers that together cover about 75% of U.S. Internet communications. They must hand over what the NSA asks for under orders from the secret Foreign Intelligence Surveillance Court. The firms search Internet traffic based on the NSA's criteria, current and former officials say.  Fist tap Arnach.