Yahoo Security Notice September 22, 2016

We have confirmed, based on a recent investigation, that a copy of certain user account information was stolen from our network in late 2014 by what we believe is a state-sponsored actor. The 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.  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 in the system that the investigation has found to be affected.

Below are FAQs containing details about this issue and steps that users can take to help protect their accounts.

What happened?

A recent investigation by Yahoo has confirmed that a copy of certain user account information was stolen from our network in late 2014 by what we believe is a state-sponsored actor. We are working closely with law enforcement authorities and notifying potentially affected users of ways they can further secure their accounts.

Was my account affected?

We are notifying potentially affected users by email and posting additional information to our website. Additionally, we are asking potentially affected users to promptly change their passwords and adopt alternate means of account verification.

Is the state-sponsored actor still in Yahoo’s network?

The ongoing investigation has found no evidence that the state-sponsored actor is currently in Yahoo’s network.

What information was stolen?

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. 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 in the system that the investigation has found to be affected.

What is a "hashed password"?

Hashing is a one-way mathematical function that converts an original string of data into a seemingly random string of characters. As such, passwords that have been hashed can’t be converted into the original plain text password.

What is "bcrypt"?

Bcrypt is a password hashing mechanism that incorporates security features, including salting and multiple rounds of computation, to provide advanced protection against password cracking.

I think I received an email about this issue. How do I know that it is really from Yahoo?

Click here to view the content of our notice to affected users. Please note that the email from Yahoo about this issue will display the Yahoo Purple Y icon icon when viewed through the Yahoo website or Yahoo Mail app. Importantly, the email does not ask you to click on any links or contain attachments and does not request your personal information. If the email you received about this issue prompts you to click on a link, download an attachment, or asks you for information, the email was not sent by Yahoo and may be an attempt to steal your personal information. Avoid clicking on links or downloading attachments from such suspicious emails.

What is Yahoo doing to protect my account?

We have taken action to protect our users, including:

  • We are notifying affected users.
  • We are asking affected users to promptly change their passwords and adopt alternate means of account verification.
  • We invalidated unencrypted security questions and answers so that they cannot be used to access an account.
  • We are recommending that all users who haven't changed their passwords since 2014 do so.
  • We continue to enhance our systems that detect and prevent unauthorized access to user accounts.
  • Our investigation into this matter continues.

How do I change my password or disable security questions and answers?

You can change your Yahoo password or security questions and answers by clicking here.

Is there anything I can do to protect myself?

We encourage all of our users to follow these security recommendations:

  • Change your password and security questions and answers for any other accounts on which you use the same or similar credentials as the ones used for your Yahoo Account.
  • Review your accounts for suspicious activity.
  • Be cautious of any unsolicited communications 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.

Additionally, please consider using Yahoo’s Account Key, a simple authentication tool that eliminates the need to use a password altogether.

Are Tumblr accounts affected?

No. The systems from which the data was stolen contained no Tumblr user data at the time of the theft.

How can I get help with my account?

If you need further information or assistance with your account, please visit https://help.yahoo.com, where you will find the latest information and may be able to access direct customer support. Please DO NOT ENGAGE with fraudulent online fee-based, toll-free-number services PRETENDING to be Yahoo support. Please note: Yahoo channels all support through https://help.yahoo.com.