State-sponsored hacker stole data of 500 million Yahoo users

Previous reports talked about hacked data of 200 million users, but it turns out the data breach at Yahoo is much bigger than previously thought. Yahoo just confirmed it was the victim of a security breach in late 2014 and that data of over 500 million user accounts was stolen. Not just the scale of the hack, which is believed to be the largest ever, is stunning, it's also quite surprising who Yahoo believes to be behind the attack.

The Internet company claims the hack was performed by a state-sponsored actor and notes personal data including names, e-mail addresses, phone numbers, dates of birth, weakly encrypted passwords, and encrypted and unencrypted security questions and answers may have been stolen. Yahoo stresses the attacker did not have access to payment card data or bank account information.

Yahoo users who have not changed their password since 2014 should change it right now, as well as the password of any other accounts that share the same password.

A recent investigation by Yahoo! Inc. (NASDAQ:YHOO) has confirmed that a copy of certain user account information was stolen from the company’s network in late 2014 by what it believes is a state-sponsored actor. The account information may have included names, email addresses, telephone numbers, dates of birth, hashed passwords (the vast majority with bcrypt) and, in some cases, encrypted or unencrypted security questions and answers. The ongoing investigation suggests that stolen information did not include unprotected passwords, payment card data, or bank account information; payment card data and bank account information are not stored in the system that the investigation has found to be affected. Based on the ongoing investigation, Yahoo believes that information associated with at least 500 million user accounts was stolen and the investigation has found no evidence that the state-sponsored actor is currently in Yahoo’s network. Yahoo is working closely with law enforcement on this matter.

Yahoo is notifying potentially affected users and has taken steps to secure their accounts. These steps include invalidating unencrypted security questions and answers so that they cannot be used to access an account and asking potentially affected users to change their passwords. Yahoo is also recommending that users who haven’t changed their passwords since 2014 do so.

Yahoo encourages users to review their online accounts for suspicious activity and to change their password and security questions and answers for any other accounts on which they use the same or similar information used for their Yahoo account. The company further recommends that users avoid clicking on links or downloading attachments from suspicious emails and that they be cautious of unsolicited communications that ask for personal information. Additionally, Yahoo asks users to consider using Yahoo Account Key, a simple authentication tool that eliminates the need to use a password altogether.

Online intrusions and thefts by state-sponsored actors have become increasingly common across the technology industry. Yahoo and other companies have launched programs to detect and notify users when a company strongly suspects that a state-sponsored actor has targeted an account. Since the inception of Yahoo’s program in December 2015, independent of the recent investigation, approximately 10,000 users have received such a notice.

I don't think they'll be toasting at Yahoo, but they now have the questionable honor of being the victim of world's largest data breach. The previous record holder was MySpace, with over 359 million accounts breached.