Where's Waldo? Ask the NSA.

That's right, you can add location tracking to the list of surveillance activities being carried out by the secretive US National Security Agency.

Citing documents from the trove leaked by former agency contractor Edward Snowden, as well as statements from US intelligence officials, The Washington Post reports that the agency is sucking up "5 billion records a day on the whereabouts of cell phones around the world" and storing location info on "at least hundreds of millions of devices."

And though US citizens aren't targeted by the program (according to the NSA, which also says the program is legal), location data on an unspecified number of Americans in the States does get captured, the Post reports.

"Analysts can find cell phones anywhere in the world, retrace their movements, and expose hidden relationships among individuals using them," the Post writes, adding later that the most basic analytic tools used in the program "map the date, time, and location of cell phones to look for patterns or significant moments of overlap. Other tools compute speed and trajectory for large numbers of mobile devices, overlaying the electronic data on transportation maps to compute the likely travel time and determine which devices might have intersected."

Though it's perhaps alarming, news of such a program isn't necessarily surprising. In October, The New York Times revealed that the NSA had tested, in 2010 and 2011, its systems' ability to handle bulk data on the location of Americans' cell phones. Both Director of National Intelligence James Clapper and NSA chief Keith Alexander told Congress then that the data was used only for the test and "was not used for any other purpose and was never available for intelligence analysis purposes." Alexander added that location tracking "may be something that is a future requirement for the country."

However, Sen. Ron Wyden (D-Ore.), who's privy to classified info as a member of the Senate Intelligence Committee and has been critical of the NSA's surveillance programs, hinted that tracking might well be taking place. "Once again, the intelligence leadership has decided to leave most of the real story secret -- even when the truth would not compromise national security," he said at the time.

The newly revealed program -- which involves analytic tools collectively known as CO-TRAVELER -- nabs location data, i.e., cell tower identifiers, by tapping into the cables that tie together mobile networks around the world, the Post reports.

The Post mentions two corporate partners involved in the collection, which are identified in the Snowden documents only as ARTIFICE and WOLFPOINT. But the paper quotes Matt Blaze, an associate professor of computer and information science at the University of Pennsylvania, as saying that an intelligence agency can "get 'one stop shopping' to an expansive range of subscriber data just by compromising a few carriers." That's because carriers share entire databases of customer info to handle situations like roaming, so a carrier could have access to data about other carriers' customers.

The general counsel for the Office of the Director of National Intelligence, which oversees the NSA, told the Post that phones in the US are not the quarry. "There is no element of the intelligence community that under any authority is intentionally collecting bulk cell phone location information about cell phones in the United States," Robert Litt said.

Regardless, the American Civil Liberties Union, a vocal opponent of the NSA's mass-surveillance programs, decried the warrantless data collection.

"The paths that we travel every day can reveal an extraordinary amount about our political, professional, and intimate relationships," the organization said in a statement. "The dragnet surveillance of hundreds of millions of cell phones flouts our international obligation to respect the privacy of foreigners and Americans alike. The government should be targeting its surveillance at those suspected of wrongdoing, not assembling massive associational databases that by their very nature record the movements of a huge number of innocent people."

You can check out the Post's full report, including detailed infographics, here.

Update, 3 p.m. PT: Adds statement from ACLU.