One Million Accounts Breached In Latest Yahoo Hack

Yahoo has disclosed that another large breach has occurred in their systems in August 2013 and has resulted in the harvesting of more than one billion accounts.

One Billion Users Affected In Yet-Another Yahoo Breach

Yahoo has faced another very large breach after a security investigation. The company publicly disclosed in a blog post that that they have noticed a breach of their data that occurred in August 2013. More than one billion user accounts are affected by the incident. An investigation into the issue is ongoing as Yahoo has not been able to identify the individual or the group behind the intrusion. The company believes that this breach is not related to the previous large incident.

Once again the breach likely contains the same information – usernames, associated email addresses, birth dates, and the hashed MD5 passwords, as well as the encrypted and unencrypted security answers.

Yahoo has issued a new mandatory password reset for some of the affected users. The Yahoo staff have said that no cleartext passwords or payment card details were not breached. In addition the company has stated that they have also invalidated the unencrypted security questions and answers as an extra security precaution.

The proprietary Yahoo code was by the attackers to forge cookies that were used to fool the security system.

Yahoo has advised their users to follow the standard recommendations that are used when such incidents occur:

  • Affected users should change their passwords and security questions and answers for all accounts that are shared with other online accounts.
  • All account should be reviewed for suspicious activity
  • Users should be cautious of any messages or sites that might ask for personal information
  • Clicking or downloading attachments from suspicious emails should be avoided
  • Yahoo users should opt to use the Yahoo Account Key authentication tool

Here is an excerpt of Yahoo’s notification:

What happened?

As we previously disclosed in November, law enforcement provided us with data files that a third party claimed was Yahoo user data. We analysed this data with the assistance of outside forensic experts and found that it appears to be Yahoo user data. Based on further analysis of this data by the forensic experts, we believe an unauthorised third party, in August 2013, stole data associated with more than one billion user accounts. We have not been able to identify the intrusion associated with this theft. We believe this incident is likely distinct from the incident we disclosed on September 22, 2016.

For potentially affected accounts, 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 stolen information 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 the company believes was affected.

Separately, we previously disclosed that our outside forensic experts were investigating the creation of forged cookies that could allow an intruder to access users’ accounts without a password. Based on the ongoing investigation, we believe an unauthorised third party accessed our proprietary code to learn how to forge cookies. The outside forensic experts have identified user accounts for which they believe forged cookies were taken or used. We are notifying the affected account holders, and have invalidated the forged cookies. We have connected some of this activity to the same state-sponsored actor believed to be responsible for the data theft the company disclosed on September 22, 2016.

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Author : Martin Beltov

Martin graduated with a degree in Publishing from Sofia University. As a cyber security enthusiast he enjoys writing about the latest threats and mechanisms of intrusion.

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