WASHINGTON — The National Security Agency is harvesting hundreds of millions of contact lists from personal e-mail and instant-messaging accounts around the world, many of them belonging to Americans, according to senior intelligence officials and top secret documents provided by former NSA contractor Edward Snowden.
The collection program, which has not been disclosed before, intercepts e-mail address books and ‘‘buddy lists’’ from instant-messaging services as they move across global data links. Online services often transmit those contacts when a user logs on, composes a message, or synchronizes a computer or mobile device with information stored on remote servers.
Rather than targeting individual users, the NSA is gathering contact lists in large numbers that amount to a sizable fraction of the world’s e-mail and instant-messaging accounts. Analysis of that data enables the agency to search for hidden connections and map relationships within a much smaller universe of foreign intelligence targets.
During a single day last year, the NSA’s Special Source Operations branch collected 444,743 e-mail address books from Yahoo, 105,068 from Hotmail, 82,857 from Facebook, 33,697 from Gmail, and 22,881 from unspecified other providers, according to an internal NSA PowerPoint presentation. Those figures, described as a typical daily intake in the document, correspond to a rate of more than 250 million per year.
Each day, the presentation said, the NSA collects contacts from an estimated 500,000 buddy lists on live-chat services as well as from the ‘‘in-box’’ displays of Web-based e-mail accounts.
The collection depends on secret arrangements with foreign telecommunications companies or allied intelligence services in control of facilities that direct traffic along the Internet’s main data routes.
Although the collection takes place overseas, two senior US intelligence officials acknowledged that it sweeps in the contacts of many Americans. They declined to offer an estimate but did not dispute that the number is likely to be in the millions or tens of millions.
The data could enable the NSA to draw detailed maps of a person’s life, as told by professional, political, and religious connections.
A spokesman for the Office of the Director of National Intelligence, which oversees the NSA, said the agency ‘‘is focused on discovering and developing intelligence about valid foreign intelligence targets like terrorists, human traffickers, and drug smugglers. We are not interested in personal information about ordinary Americans.’’
The spokesman, Shawn Turner, added that rules approved by the attorney general require the NSA to ‘‘minimize the acquisition, use, and dissemination’’ of information that identifies a US citizen or permanent resident.
The NSA’s collection of nearly all US call records, under a separate program, has generated significant controversy since it was revealed in June. The NSA’s director, General Keith Alexander, has defended ‘‘bulk’’ collection as an essential counterterrorism and foreign intelligence tool, saying ‘‘you need the haystack to find the needle.’’
Contact lists stored online provide the NSA with far richer sources of data than call records alone.
Address books commonly include not only names and e-mail addresses but also telephone numbers, street addresses, and business and family information. In-box listings of e-mail accounts stored in the ‘‘cloud’’ sometimes contain content such as the first few lines of a message.
Taken together, the data would enable the NSA, if permitted, to draw detailed maps of a person’s life, as told by personal, professional, political, and religious connections. The picture can also be misleading, creating false ‘‘associations’’ with ex-spouses or people with whom an account holder has had no contact in many years.
The NSA has not been authorized by Congress or the special intelligence court that oversees foreign surveillance to collect contact lists in bulk, and senior intelligence officials said it would be illegal to do so from facilities in the United States. The agency avoids the restrictions in the Foreign Intelligence Surveillance Act by intercepting contact lists from access points ‘‘all over the world,’’ one official said, speaking on the condition of anonymity to discuss a classified program. ‘‘None of those are on US territory.’’
Because of the method employed, the agency is not legally required or technically able to restrict its intake to contact lists belonging to specified foreign intelligence targets, he said.
When information passes through ‘‘the overseas collection apparatus,’’ the official added, ‘‘the assumption is you’re not a US person.’’
In practice, data from Americans is collected in large volumes — in part because they live and work overseas, but also because data crosses international boundaries even when its American owners stay at home. Large technology companies, including Google and Facebook, maintain data centers around the world to balance loads on their servers and work around outages.
A senior US intelligence official said that the privacy of Americans is protected, despite mass collection, because ‘‘we have checks and balances built into our tools.’’
NSA analysts, he said, may not search or distribute information from the contacts database unless they can ‘‘make the case that something in there is a valid foreign intelligence target in and of itself.’’
In this program, the NSA is obliged to make that case only to itself or others in the executive branch. With few exceptions, intelligence operations overseas fall solely within the president’s legal purview. The Foreign Intelligence Surveillance Act, enacted in 1978, imposes restrictions only on electronic surveillance that targets Americans or takes place on US territory.
By contrast, the NSA draws on authority in the Patriot Act for its bulk collection of domestic phone records.