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Yahoo Announced Another Massive Data Breach. Has Begun Notifying Affected Users

Yahoo logo Yahoo announced on Wednesday a new data breach that affected as many as one billion users. The company believes this latest breach is different from its September 2016 breach. After law enforcement notified Yahoo in November about data files a third party claimed were stolen during the latest breach:

"... The company analyzed 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, Yahoo believes an unauthorized third party, in August 2013, stole data associated with more than one billion user accounts. The company has not been able to identify the intrusion associated with this theft. Yahoo believes this incident is likely distinct from the incident the company disclosed on September 22, 2016."

The data elements stolen included full names, e-mail addresses, telephone numbers, dates of birth, hashed passwords and, in some cases, encrypted or un-encrypted security questions and answers. The announcement also said that no payment card data or bank account information was stolen.

Regardless, this is bad. First, Yahoo doesn't know how the criminals hacked its systems. So, it cannot prevent another breach. Second, law enforcement notified Yahoo. It's breach detection systems failed. Third, one billion is a lot of affected users. Fourth, the data elements stolen expose affected users to spam and attempted break-ins to their other online accounts. Cyber criminals will test stolen passwords at other sites to see where else they can access. It's what they do.

Fifth, Yahoo's stock price is falling again after news broke about the latest breach. Verizon has already said it will re-evaluate its acquisition offer based upon the latest news, or it may terminate the acquisition deal entirely.

Yahoo's breach announcement also disclosed:

"Separately, Yahoo previously disclosed that its 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, the company believes an unauthorized third party accessed the company's 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. Yahoo is notifying the affected account holders, and has invalidated the forged cookies. The company has 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."

That's not good, either. The announcement did not disclose the name of the state-sponsored actor.

A reader of this blog shared the e-mail breach notice they received from Bob Lord, the Chief Information Security Officer at Yahoo. The breach notice contained much of the same content as the online announcement, but omitted the above information about forged cookies. The breach notice sent to users stated:

"From: Yahoo (Yahoo@communications.yahoo.com)
Sent: Wednesday, December 14, 2016 7:38 PM
Subject: Important Security Information for Yahoo Users

NOTICE OF DATA BREACH

Dear XXXXXXX,
We are writing to inform you about a data security issue that may involve your Yahoo account information. We have taken steps to secure your account and are working closely with law enforcement.

What Happened?
Law enforcement provided Yahoo in November 2016 with data files that a third party claimed was Yahoo user data. We analyzed 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 unauthorized third party, in August 2013, stole data associated with a broader set of user accounts, including yours. 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.

What Information Was Involved?
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. Not all of these data elements may have been present for your account. 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 we believe was affected.

What We Are Doing
We are taking action to protect our users:

  • We are requiring potentially affected users to change their passwords.
  • We invalidated unencrypted security questions and answers so that they cannot be used to access an account.
  • We continuously enhance our safeguards and systems that detect and prevent unauthorized access to user accounts.

What You Can Do
We encourage you to follow these 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 all of 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 Account Key, a simple authentication tool that eliminates the need to use a password on Yahoo altogether.

For More Information
For more information about this issue and our security resources, please visit the Yahoo Security Issues FAQs page available at https://yahoo.com/security-update.

Protecting your information is important to us and we work continuously to strengthen our defenses.

Sincerely,

Bob Lord
Chief Information Security Officer
Yahoo"

What are your opinions of the latest breach at Yahoo? Is the company doing enough to protect users' information?

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