Sunnyvale, (IANS) : Yahoo on Wednesday disclosed a new security breach that may have affected more than one billion accounts. The breach dates back to 2013 and is thought to be separate from a massive cybersecurity incident announced in September.

Yahoo now believes an “unauthorised third party” stole user data from more than one billion accounts in August 2013. That data may have included names, e-mail addresses and passwords, but not financial information, CNN reported.

The company will notify users who may be affected and has begun requiring users to change their passwords.

The security incident, likely one of the largest cybersecurity breaches ever, comes less than three months after Yahoo admitted data from at least 500 million accounts had been stolen.

That earlier breach, which Yahoo has attributed to a “state-sponsored actor”, is “likely distinct” from the newly disclosed breach, according to the company.