The NSA finally admitted Wednesday why it wants to track your phone's metadata, like the stats of who you call and when.

They're looking to see if you ever call anybody who's called anybody who's called anybody who might be of real interest.

NSA deputy director Chris Inglis told the House Judiciary Committee on Wednesday that the agency looks for "two or three hops" from a particular target's activity. That's a reference to the practice called "contact chaining," meaning that if a target has contact with somebody else, that person is worth looking at, too.

In June, The Guardian published the first of whistleblower Edward Snowden's many explosive documents: proof that the NSA issues court orders for Verizon to turn over the metadata of all American calls, in bulk, for three months at a time.

President Obama, in response to public outrage about that revelation, insisted that "no one is listening to your phone calls" without a warrant. However, in an interview with Charlie Rose, he admitted to and defended collecting Americans' metadata:

Program number one called the 215 program [referring to section 215 of the PATRIOT Act]. What that does is it gets data from the service providers—like a Verizon—in bulk. And basically you have call pairs. You have my telephone number connecting with your telephone number. There are no names, there’s no content in that database. All it is, is the number pairs, when those calls took place, how long they took place. So that database is sitting there.

That's not to say that the NSA only uses the telephone metadata to chain terrorists. And other leaked Snowden documents indicate it's possible, even quite likely, that the agency taps every major phone carrier, not just Verizon.

There's also plenty of reason to think the NSA broadly identifies targets, considering yet other leaked documents show the agency has a broad range of ways to define a target can be eligible to track.

Illustration via Jason Reed