Hackers stole info from 500 million accounts at Yahoo

SAN FRANCISCO — Computer hackers swiped personal information from at least 500 million Yahoo accounts in what is believed to be the biggest digital break-in at an email provider.

The massive security breakdown disclosed Thursday poses new headaches for beleaguered Yahoo CEO Marissa Mayer as she scrambles to close a $4.8 billion US sale to Verizon.

The breach dates back to late 2014, raising questions about the checks and balances within Yahoo — a fallen Internet star that has been laying off staff and trimming expenses to counter a steep drop in revenue during the past eight years. At the time of the breakin, Yahoo’s security team was led by Alex Stamos, a respected industry executive who left last year to take a similar job at Facebook.

Yahoo didn’t explain what took so long to uncover a heist that it blamed on a “state-sponsored actor” — parlance for a hacker working on behalf of a foreign government.

The Sunnyvale, California, company declined to explain how it reached its conclusions about the attack for security reasons, but said it is working with the FBI and other law enforcement. Yahoo began investigating a possible breach in July, around the time the tech site Motherboard reported that a hacker who uses the name “Peace” was trying to sell account information belonging to 200 million Yahoo users.

Yahoo didn’t find evidence of that reported hack, but additional digging later uncovered a far larger, allegedly state-sponsored attack.

“We take these types of breaches very seriously and will determine how this occurred and who is responsible,” the FBI said in a Thursday statement.

The Yahoo theft represents the accounts ever stolen from a single email provider, according to computer security analyst Avivah Litan with the technology research firm Gartner Inc.

“It’s a shocking number,” Litan said. “This is a pretty big deal that is probably going to cost them tens of millions of dollars. Regulators and lawyers are going to have a field day with this one.”

Yahoo said it has more than a billion monthly users, although it hasn’t disclosed how many of those people have email accounts. In July, 161 million people worldwide used Yahoo email on personal computers, a 30 per cent decline from the same time in 2014.