Yahoo!Inc. in 2015 secretly complied with a classified U.S. governmentdemand to scan Yahoo Mail accounts, Reuters reported Oct. 4, citing people withknowledge of the matter.

According to three former employees, Yahoo built a customsoftware program which searched all incoming emails for the Federal Bureau ofInvestigation or National Security Agency. It was the company's CEO, MarissaMayer, who reportedly decided to agree to the demand that came in the form of aclassified order sent to Yahoo's legal team.

Her decision caused the company's security chief toleave Yahoo in 2015,even though his resignation announcement did not make reference to any problemswith the company, according to the report. Yahoo's security team discovered theprogram in May 2015, a few weeks after its installation.

The 2008 amendments to the Foreign Intelligence SurveillanceAct empower intelligence agencies to ask U.S. internet and phone companies tohand over customer data for foreign intelligence gathering. The internetcompany reportedly agreed to search all incoming messages, not just storedmessages or a few targeted accounts.

It was not clear what information the intelligence officialssought, but they did task Yahoo with looking for a set of characters, accordingto the report. Reuters also could not establish whether or not any data washanded over.

When asked to comment, the company said: "Yahoo is a law-abidingcompany, and complies with the laws of the United States."

Companies have previously refused to comply with suchrequests, like AppleInc.'s refusal to create a backdoor to an iPhone recovered aspart of a probe into the San Bernardino, Calif., shootings earlier this year.The stance earnedsupport from variousCEOs of internet and tech companies.