American search engine giant Yahoo disclosed today that over 1 billion user accounts were stolen from its computer network in 2013. In September, the company has also announced that hackers breached into its computer systems carting away over 500 million user accounts in 2014.

In a statement, Yahoo said it is cooperating with computer forensic experts to identify the intruder is what can be considered and the biggest computer security breach in history. It said that the latest report is different from those that was disclosed on September 22, 2016.

Yahoo said that the breached may have included names, email addresses, telephone numbers, dates of birth, hashed passwords (using MD5) and, in some cases, encrypted or unencrypted security questions and answers. 

Yahoo, however, pointed out that the stolen information did not include passwords in clear text, payment card data, or bank account information. Payment card data and bank account information are not stored in the system the company believes were affected.

Yahoo called on their 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.