In 2015, Yahoo CEO Marissa Meyer ordered the company's engineers to build a tool that scanned Yahoo Mail messages in realtime for "characters" of interest to a US security agency, either the FBI or the NSA.
As far as we know, the move was unprecedented in US tech history, and it triggered the departure of then-CSO Alex Stamos (previously), now CSO for Facebook.
The demand to search Yahoo Mail accounts came in the form of a classified directive sent to the company's legal team, according to the three people familiar with the matter.
U.S. phone and Internet 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 directive for real-time Web collection or one that required the creation of a new computer program.
"I've never seen that, a wiretap in real time on a 'selector,'" said Albert Gidari, a lawyer who represented phone and Internet companies on surveillance issues for 20 years before moving to Stanford University this year. A selector refers to a type of search term used to zero in on specific information.
"It would be really difficult for a provider to do that," he added.