Yahoo Biggest Security Breach Yet at 500 Million Accounts Exposed

Yahoo's network has been hacked, and the information from "at least 500 million user accounts" was stolen.

Moreover, the information that was disclosed has been available for about two years. Bob Lord, Yahoo's CISO, stated in an announcement on Thursday that the theft had started in "late 2014 by what we believe is a state-sponsored actor."

The stolen information included "names, email addresses, telephone numbers, dates of birth, hashed passwords" and the answers to security questions. No credit card numbers were disclosed in the breach, he added. The hashed passwords mostly used bcrypt, which adds "salting and multiple rounds of computation" as part of the encryption protection scheme, according to Yahoo.

Yahoo is sending a security notice out to its subscribers urging them to change their passwords and their security questions. They should also check for suspicious account activity. Yahoo also claims that use of the Yahoo Account Key service will increase security by verifying user identities using a mobile device. More information about the breach is provided in a Yahoo FAQ.

The exposure of 500 million Yahoo accounts appears to be the largest breach yet to date. For instance, the site, run by Microsoft MVP Troy Hunt, listed the MySpace hack at 359 million accounts exposed, while LinkedIn and Adobe followed at 165 million and 152 million accounts exposed, respectively.

Verizon announced the purchase of Yahoo in late July for an estimated $4.8 billion. However, press accounts (such as this one from BBC News) cited Verizon as indicating that it only got notification of the massive breach two days earlier than Yahoo's public announcement today.

The breach is said to have come to Yahoo's attention after an Aug. 1 Motherboard story reported that Yahoo's stolen information was being offered up for sale by a hacker.

About the Author

Kurt Mackie is senior news producer for the 1105 Enterprise Computing Group.


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