Yahoo may have allowed US government to search user emails

Yahoo Inc a year ago secretly built a custom software program to search all of its customers' incoming emails for specific information provided by United States intelligence officials, according to people familiar with the matter.

It is said to be the first time a US internet company has been caught searching all incoming messages on behalf of a spy agency. But the company was querying for a "set of characters", possibly a phrase in an email or attachment, according to Reuters.

The request was sent to Yahoo's legal team in a classified directive, Reuters reported.

The cooperation with the government's spying on emails created a rift between Stamos and Yahoo CEO Marissa Mayer, prompting Stamos to leave in June 2015, according to Reuters.

Those individuals told Reuters that the government pushed Yahoo to search for a string of letters, numbers or other characters. It had thought the company had been hacked.

Image courtesy of Yahoo Inc.

The mass email searches might go above and beyond other US government requests for information. Both the NSA and the Federal Bureau of Investigation didn't immediately respond to a request for comment.

The Foreign Intelligence Surveillance Court, which authorizes the government's surveillance requests, signed off on the unusual request, which is thought to be the first of its kind. The report also said that a programming flaw could have allowed hackers into the stored emails. "For a company to secretly search all incoming email of all its customers in a response to a broad government directive would be a blow to privacy and a serious threat to freedom of expression".

"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", Toomey continued.

As the executives chose to bypass the company's own security team, the discovery of the program by Yahoo's own employees led to internal tension and apparently resulted in the departure of Stamos from the company, who has since joined Facebook as its top security expert.

Additionally, Verizon is in the process of acquiring Yahoo in a deal worth around $4.8 million.

In a separate incident, Yahoo last month said "state-sponsored" hackers had gained access to 500 million customer accounts in 2014.