We are writing to inform you about a data security issue that may involve your Yahoo account information.
A recent investigation by Yahoo has confirmed that a copy of certain user account information was stolen from our systems in late 2014 by what we believe is a state-sponsored actor. We are closely coordinating with law enforcement on this matter and working diligently to protect you.
What information was involved?
The stolen user account information may have included names, email addresses, telephone numbers, dates of birth, hashed passwords (the vast majority with bcrypt) and, in some cases, encrypted or unencrypted security questions and answers. Not all of these data elements may have been present for your account. The ongoing investigation suggests that stolen information did not include unprotected passwords, payment card data or bank account information; payment card data and bank account information are not stored on the system that the investigation has found to be affected.
What we are doing
We are taking action to protect our users:
We are asking potentially affected users to promptly change their passwords and adopt alternative means of account verification.
We invalidated unencrypted security questions and answers so they cannot be used to access an account.
We are recommending all users who have not changed their passwords since 2014 to do so.
We continue to enhance our systems which detect and prevent unauthorised access to user accounts.
We are working closely with law enforcement on this matter.
Our investigation into this matter is ongoing.
What you can do
We encourage you to follow these security recommendations:
Change your password and security questions and answers for any other accounts on which you used the same or similar information used for your Yahoo account.
Review your accounts for suspicious activity.
Exercise caution with any unsolicited forms of communication that ask for your personal information or refer you to a web page asking for personal information.
Avoid clicking on links or downloading attachments from suspicious emails.
In addition, please consider using Yahoo Account Key, a simple authentication tool that completely eliminates the need to use a password.