The National Security Agency $($NSA$),$ an intelligence agency of the U$.$S$.$ government, is responsible for the making and breaking of codes used to encrypt sensitive communications, and for the interception of signals on behalf of the federal government. The information generated and intercepted by the NSA is used for intelligence and counterintelligence purposes and to support U$.$S$.$ military operations.

The NSA has established a comprehensive telecommunications network capable of monitoring billions of emails and phone calls$$whether they originate within the United States or overseas. AT&T$$s powerful ground$-$based communications stations, which are used to relay messages to communications satellites, are a major component of the NSA network; that includes three $105-$ foot dishes in rural Pennsylvania that relay most U$.$S$.$ communications to and from Europe and the Middle East and three similar dishes in California that handle communications for the Pacific Rim and Asia. It has been estimated that the NSA also has anywhere from ten to twenty secret listening posts, which the agency can use to tap into the telecommunications switches of other U$.$S$.$ telecom carriers to capture domestic traffic traveling over these networks.

The Advanced Encryption Standard $($AES$)$ algorithm is the current state$-$of$-$the$-$art standard for encrypting top$-$secret communications. According to experts, it would take approximately $12$ billion years to break this code via a trial$-$and$-$error brute force attack using today$$s supercomputers. However, in recent years, the NSA has made vast breakthroughs in its ability to crack codes. The agency is employing advanced technology to build super$-$fast computers and sophisticated software $$capable of breaking the AES encryption key within an actionable time period.$$ Such research has been going on since at least $2004$ at a computer research center in Oak Ridge, Tennessee, where the goal is to build a supercomputer that can operate at phenomenal rate of $1018$ operations per second.

Once an encrypted message is broken, software created by a company called Narus, part of Boeing, searches it for target addresses, locations, countries, and phone numbers, as well as certain names, keywords, and phrases on NSA$$s watch list. Suspicious communications are recorded and then transmitted to other locations where it can be stored and, if need be$,$ accessed by NSA code breakers, data miners, intelligence analysts, counterterrorism specialists, and others. One of those locations is a new $$1\mathrm{.}5$ billion, one million square foot data center located in Utah. It boasts a prodigious data storage capacity measured in units of yottabytes $(1024$ bytes$).$ This is more than enough capacity to store the current global volume of all Internet traffic for a thousand years.

By law, NSA$$s intelligence gathering is limited to the interception of foreign communications. Intelligence activities involving U$.$S$.$ citizens and activities conducted within the United States require special consideration because those activities could violate privacy rights and civil liberties guaranteed under the Fourth Amendment and other laws. Various advocacy groups, including the American Civil Liberties $($ACLU$),$ the Center for Democracy and Technology $($CDT$),$ and the Electronic Frontier Foundation $($EFF$),$ have expressed concern that government agencies, including the NSA, are conducting extensive surveillance of both foreign nationals and millions of Americans.

In early $2012,$ NSA chief General Keith Alexander testified in front of the House Armed Services subcommittee on Emerging Threats and Capabilities and denied that the NSA had the capability to monitor, inside the United States, Americans$$ text messages, phone calls, and emails. However, the NSA has not always been entirely forthcoming about its activities. In late $2005,$ an article in the New York Times revealed that President George W$.$ Bush had secretly authorized the NSA to conduct warrantless eavesdropping on thousands of Americans beginning in $2002.$