Hackers Stole Data From 1 Billion Users Accounts From Yahoo, Company Says

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NEW YORK — Yahoo says it believes hackers stole data from more than one billion user accounts in August 2013.

The Sunnyvale, California, company says it’s a different breach from the one it disclosed in September, when it said 500 million accounts were exposed. In a statement, Yahoo said they believe “some of this activity to the same state-sponsored actor” responsible for the Sept. hack.

“Separately, Yahoo previously disclosed that its outside forensic experts were investigating the creation of forged cookies that could allow an intruder to access users’ accounts without a password. Based on the ongoing investigation, the company believes an unauthorized third party accessed the company’s proprietary code to learn how to forge cookies,” the statement reads. “The outside forensic experts have identified user accounts for which they believe forged cookies were taken or used. Yahoo is notifying the affected account holders, and has invalidated the forged cookies.”

That new hack revelation raises questions about whether Verizon will try to change the terms of its $4.8 billion proposed acquisition of Yahoo.

Yahoo says the information stolen may include names, email addresses, phone numbers, birthdates and security questions and answers. The company says it believes bank-account information and payment-card data were not affected.

Yahoo recommended users review their accounts for suspicious activity, change their passwords and avoid clicking on links in emails from unsolicited emails.