FBI is investigating massive Yahoo breach

WASHINGTON—The FBI has launched an investigation into a massive breach of Yahoo's systems that may have resulted in data theft involving more than 1 billion user accounts, the White House said Thursday

White House Press Secretary Josh Earnest declined to elaborate on the extent of the inquiry into the 2013 intrusion, the second time this year the company has acknowledged an extensive compromise of data.

In September, Yahoo disclosed a 2014 intrusion involving some 500 million accounts.

Yahoo said in September that evidence linked the 500 million-account hack to a state-sponsored attacker, though it did not identify the government. Responsibility for the larger intrusion has not been determined, and the company believed the two are not linked.

The FBI, which had previously acknowledged it had opened an inquiry related to the company's September disclosure, declined to comment further.

“We take these types of breaches very seriously and will determine how this occurred and who is responsible,'' the FBI said at that time. "We will continue to work with the private sector and share information so they can safeguard their systems against the actions of persistent cyber criminals.”