National Security Agency (NSA) headquarters
National Security Agency (NSA) headquartersReuters

The National Security Agency (NSA) has built a surveillance system capable of recording “100 percent” of a foreign country’s telephone calls and enabling the agency to rewind and review conversations as long as a month after they take place, The Washington Post reported on Tuesday.

The report is based on sources with direct knowledge of the effort and documents supplied by former contractor Edward Snowden.

A senior manager for the program compared it to a time machine that can replay the voices from any call without requiring that a person be identified in advance for surveillance.

The voice interception program, called MYSTIC, began in 2009, according to The Washington Post. Its RETRO tool, short for “retrospective retrieval,” and related projects reached full capacity against the first target nation in 2011. Planning documents two years later anticipated similar operations elsewhere.

In the initial deployment, collection systems are recording “every single” conversation nationwide, storing billions of them in a 30-day rolling buffer that clears the oldest calls as new ones arrive, according to a classified summary.

The call buffer opens a door “into the past,” the summary says, enabling users to “retrieve audio of interest that was not tasked at the time of the original call.” Analysts listen to only a fraction of 1 percent of the calls, but the absolute numbers are high. Each month, they send millions of voice clippings, or “cuts,” for processing and long-term storage, according to the report.

At the request of U.S. officials, The Washington Post withheld details that could be used to identify the country where the system is being employed or other countries where its use was envisioned.

In a statement, Caitlin Hayden, spokeswoman for the National Security Council, declined to comment on “specific alleged intelligence activities.”

Speaking generally, Hayden told the newspaper that “new or emerging threats” are “often hidden within the large and complex system of modern global communications, and the United States must consequently collect signals intelligence in bulk in certain circumstances in order to identify these threats.”

NSA spokeswoman Vanee Vines, in an e-mailed statement, said that “continuous and selective reporting of specific techniques and tools used for legitimate U.S. foreign intelligence activities is highly detrimental to the national security of the United States and of our allies, and places at risk those we are sworn to protect.”

The report is the latest in a series of revelations related to the NSA’s spying program. Snowden’s leaks revealed a global surveillance system of unprecedented proportions, and sparked controversy between the U.S. and foreign leaders that had their privacy breached. 

Even Israel is not immune from surveillance, as recently leaked Snowden documents showed that the U.S. had been monitoring the email traffic of Israeli officials, including former Prime Minister Ehud Olmert and former Defense Minister Ehud Barak.

It has also been reported that the NSA recorded millions of phone calls in France, including calls involving individuals with no links to terrorism, and that the agency had collected almost 200 million text messages a day from across the globe, using them to extract data including location, contact networks and credit card details.

In addition, documents leaked by Snowden show that the NSA used social media networks such as Facebook and popular games such as Angry Birds to collect data about individuals.

Vines, in her statement, told The Washington Post that the NSA’s work is “strictly conducted under the rule of law.”

In January, President Barack Obama announced reforms in the surveillance programs of the NSA.

He proposed new protections for foreigners caught in U.S. data collection programs, which harvest hundreds of millions of pages of data on telephone calls, Internet use and text messages across the globe.