Yahoo: All 3 Billion Accounts Affected by 2013 Data Breach

Yahoo: All 3 Billion Accounts Affected by 2013 Data Breach

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Yahoo has confirmed that a 2013 data breach affected 3 billion of its accounts – three times the number previously announced in 2016.

The company updated its users on Wednesday, October 4, 2017 about the data security issue previously announced in December 2016 when it said that it believed more than one billion user accounts may have had data stolen in a cyberattack in 2013.

The disclosure came from Oath, a subsidiary of US telecomms company Verizon, which acquired Yahoo’s online assets in June 2016 for $4.48bn. However, Yahoo said it already took certain actions in 2016 to help secure its users’ accounts in connection with this issue.

The purchase price had been cut after revelations of the 2013 data breach and another in 2014 which affected 500 million accounts and resulted in charges for Russian intelligence operatives and a pair of hackers.

Regarding the 2013 breach, Oath and Verizon said the additional user accounts it had identified as potentially affected were being notified.

It was reported that after Yahoo was acquired by Verizon, the company “recently obtained additional information and, after analyzing it with the assistance of outside forensic experts, they have determined that more users’ account information also was likely affected.”

They added: “While this is not a new security issue, Yahoo is sending email notifications to the additional affected user accounts.”

What Information Was Involved?

Yahoo said, “The stolen user account information 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… The investigation indicates that the information that was stolen 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 we believe was affected.”

What Yahoo is Doing

Yahoo said they already took action to protect users beyond those identified in 2016 as potentially affected. Specifically:

  • Yahoo required potentially affected users to change their passwords.
  • Yahoo also required all other users who had not changed their passwords since the time of the theft to do so.
  • Yahoo invalidated unencrypted security questions and answers so they cannot be used to access an account.

The company said they are closely coordinating with law enforcement on this matter, and they will continue to enhance their systems that detect and prevent unauthorized access to user accounts.

What Yahoo Users Can Do

Yahoo, however, advised its user to consider the following account security recommendations:

  • Change your passwords 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.
  • 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.

In addition to the above, Yahoo encouraged its users to consider using Yahoo Account Key, a simple authentication tool that eliminates the need to use a password on Yahoo altogether

Chandra McMahon, chief information security officer at Verizon, said: “Our investment in Yahoo is allowing that team to continue to take significant steps to enhance their security, as well as benefit from Verizon’s experience and resources.”

As reported on Sky News, “The Yahoo breach is believed to be the largest in terms of the number of people affected, although the recently revealed hack at credit agency Equifax is seen as more damaging due to the sensitive nature of data gained.”


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