This information comes from Rep. Jerrold Nadler, a New York Democrat who revealed last week the NSA's briefing on Capitol Hill. Nadler was stunned to hear that the only thing required for the NSA to listen in on your calls is an analyst's approval and does not require prior legal authorization. The NSA's annual budget is undisclosed but is believed to be in the range of $10 billion which allows the agency to own the technology giving it the ability to record all domestic and international calls.
According to a published report, the NSA has a listening post in Utah that enables it to go through billions of phone calls whether the call was originated in the U.S. or internationally. Carriers like AT&T that allow the agency to comb its servers, receive immunity from civil or criminal liability thanks to a law passed in 2008 which was renewed four years later. And while the law says that the NSA "may not intentionally target any person known at the time of acquisition to be located in the United States," some legal experts say that this can be interpreted to say that the NSA can grab as much domestic information as it wants, as long as it wasn't targeting a particular person.
UPDATE: According to information from the AP, fewer than 300 phone numbers were checked by the NSA program and the program prevented terrorist activity in more than 20 countries. In addition, the Obama administration has clarified earlier information and says that despite Congressman Nadler's initial comments, a warrant is still required for law enforcement officials to listen in to your phone calls. However, theNSA can, with this approval, listen in to complete conversations and receive more than just the metadata involving a phone call.