Yahoo said Wednesday that 1 billion user accounts — meaning most of the Internet giant’s customers worldwide — were hacked by a “state-sponsored” attacker in 2013, leading to the release of user names, telephone numbers, dates of birth and other personal information. The technology giant said it believes the attack is "distinct" from another cyber attack the company reported in September this year, which involved around 500 million accounts and was said to have been carried out by a "state-sponsored actor" in late 2014. We will review the impact of this new development before reaching any final conclusions.”

Regarding the deal, Yahoo said in a statement, “We are confident in Yahoo’s value and we continue to work towards integration with Verizon.” "As Yahoo previously disclosed in November, law enforcement provided the company with data files that a third party claimed was Yahoo user data. The company said it believed this incident is likely distinct from the breach it disclosed in September, when information associated with at least 500 million user accounts was stolen from its network in 2014. Yahoo was tentative in its description of new problems, saying the incident was "likely" distinct from the one it reported in September and that stolen information "may have included" names, e-mail addresses, telephone numbers, dates of birth, hashed passwords and, in some cases, encrypted or unencrypted security questions and answers. “Yahoo encourages users to review all of their online accounts for suspicious activity and to change their passwords 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 said in a statement. Separately, Yahoo, which had 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, said Wednesday it believes an unauthorized third party accessed the company’s proprietary code to learn how to forge cookies.
Yahoo! announces that ID information about more than 1 billion accounts may have been hacked in August 2013. This is separate from the company's earlier disclosure of a data breach of 500,000 accounts in 2014.