2016.12.1423:49:00UTC+00Yahoo Discloses Newly Uncovered Massive Security Breach

Yahoo announced on Wednesday that it has discovered another cyber attack involving the hacking of the data of over one billion user accounts in August 2013, making it the biggest security breach in history.

Hackers who have not yet been identified reportedly infiltrated Yahoo's network in August 2013 and stole substantial personal data such as names, emails, addresses, phone numbers, birth dates and passwords. The disclosed 2013 hack is separate and twofold the size of the hack in 2014 that Yahoo publicized earlier this year.

Yahoo said it is notifying affected users and has invalidated the forged cookies that enables an intruder to access users' accounts without password verification. Shares of the firm fell 2% in late hours trading to $39.91.

The newly uncovered data breach which compromises Verizon's planned $4.83 billion acquisition of the internet firm. The deal was announced in July and is scheduled to be closed in early 2017. In October, after acknowledging the 2014 breach, Verizon indicated it could consider the theft incident to be a material event that could allow it to change the deal's terms.

After the latest disclosure, Verizon stated it will assess the implication of the new development before finalizing any decisions.