Tech giant Yahoo recorded the largest data breach in history on Thursday as it disclosed that a hacking took place in 2014 by “state-sponsored actors”, which may have affected 500 million accounts.

Yahoo informed its customers about the breach, requesting them to change their passwords and adopt other protective measures. The company’s Chief Information Security Officer Bob Lord said that Yahoo doesn’t think that the “state-sponsored actor” is currently in the company’s network, but was asking users to change their passwords to secure their accounts anyway.

Interestingly, the breach happened way back in 2014, but Yahoo learnt of it in July this year, and informed its customers only on Thursday.

If you are a Yahoo user, it is a good idea to change your password and security questions and answers. In case you use the same questions and passwords for other accounts, you need to change them. According to Yahoo, users should monitor their accounts for suspicious activities, and be wary of emails asking for personal information.

Yahoo is also urging its users to use “Yahoo Account Key”, an authentication tool that does away with the need to use a password at all.