The National Security Agency has the capability to record "100 percent" of the telephone calls placed in a foreign country and play them back up to a month later, according to a report Tuesday by The Washington Post.
Known as MYSTIC, the surveillance system dates back to 2009, according to documents supplied to the newspaper by former NSA contractor Edward Snowden. The program, which wasn't fully operational until 2011, intercepts and records and stores billions of calls for 30 days on a rolling buffer that purges the oldest recordings as new ones arrive, according to one classified summary cited by the newspaper.
The Post said it withheld, at the request of US officials, the identity of the targeted nation and other nations where the program's use was envisioned.
The revelation is just the latest to emerge from a trove of confidential documents leaked to the media by Snowden, detailing the NSA's controversial surveillance programs. Previous revelations showed how the NSA collected metadata associated with phone calls; this program reportedly extends surveillance to the content of conversations.
Earlier reports have indicated that the NSA has the ability to record nearly all domestic and international phone calls. Wired magazine disclosed in 2012 that the NSA has established "listening posts" that allow the agency to collect and sift through billions of phone calls through a massive new data center in Utah, "whether they originate within the country or overseas."
The NSA declined to discuss the existence of the MYSTIC recording program but insisted that all of the agency's operations strictly adhere to the rule of law.
"NSA does not conduct signals intelligence collection in any country, or anywhere in the world, unless it is necessary to advance US national security and foreign policy interests and to protect its citizens and the citizens of its allies and partners from harm," NSA spokesperson Vanee Vines said in an email.
Civil libertarians said the revelation raised fresh concerns over the NSA's surveillance capabilities.
"This is a truly chilling revelation, and it's one that underscores how high the stakes are in the debate we're now having about bulk surveillance," Jameel Jaffer, American Civil Liberties Union deputy legal director, said in a statement. "The NSA has always wanted to record everything, and now it has the capacity to do so."