SAN FRANCISCO • Yahoo Inc last year secretly built a custom program to search all of its customers' incoming e-mails for specific information provided by United States intelligence officials, according to people familiar with the matter.
The company complied with a classified US government demand, scanning hundreds of millions of Yahoo Mail accounts at the behest of the National Security Agency (NSA) or Federal Bureau of Investigation (FBI), said three former employees and a fourth person apprised of the events.
Some surveillance experts said this represents the first case to surface of a US Internet firm agreeing to an intelligence agency's request by searching all arriving messages, as opposed to examining stored messages or scanning a small number of accounts in real time.
It is not known what information intelligence officials were looking for, only that they wanted Yahoo to search for a set of characters, said the sources, who did not want to be identified.
According to two of the former employees, Yahoo chief executive Marissa Mayer's decision to obey the directive roiled some senior executives and led to the departure in June last year of chief information security officer Alex Stamos.
FEELING LET DOWN
It is deeply disappointing that Yahoo declined to challenge this sweeping surveillance order, because customers are counting on technology companies to stand up to novel spying demands in court.
MR PATRICK TOOMEY, an attorney with the American Civil Liberties Union.
The sources said the program was discovered by Yahoo's security team in May last year, within weeks of its installation. The security team initially thought hackers had broken in. When Mr Stamos found out that Ms Mayer had authorised the program, he resigned and told subordinates that he had been left out of a decision that hurt users' security, the sources said. Due to a programming flaw, he told them hackers could have accessed the e-mails.
Mr Stamos declined a request for an interview. The NSA referred questions to the Office of the Director of National Intelligence, which declined to comment.
The request to search Yahoo Mail accounts came in the form of a classified edict sent to the company's legal team, according to the three people familiar with the matter.
Ms Mayer and other executives ultimately decided to comply with the directive last year rather than fight it, in part because they thought they would lose, said the sources.
"Yahoo is a law-abiding company, and complies with the laws of the United States," Yahoo said in a statement in response to Reuters' questions about the demand. Yahoo declined any further comment.
Reuters was unable to determine what data Yahoo may have handed over, if any, and if intelligence officials had approached other e-mail providers besides Yahoo with this kind of request.
US phone and Web companies are known to have handed over bulk customer data to intelligence agencies. But some former government officials and private surveillance experts said they had not previously seen either such a broad demand for real-time Web collection or one that required the creation of a new computer program. Experts said it was likely that the NSA or FBI had approached other Internet companies with the same demand.
"It is deeply disappointing that Yahoo declined to challenge this sweeping surveillance order, because customers are counting on technology companies to stand up to novel spying demands in court," Mr Patrick Toomey, an attorney with the American Civil Liberties Union, said in a statement.
Alphabet Inc's Google and Microsoft Corp separately said on Tuesday that they had not conducted such e-mail searches.