Yahoo has discovered a three-year old security breach that enabled a hacker to compromise more than 1 billion user accounts, breaking the company's own humiliating record for the biggest security breach in history.

The digital heist disclosed on Wednesday occurred in August 2013, more than a year before a separate hack that Yahoo announced nearly three months ago. That breach affected at least 500 million users, which had been the most far-reaching hack until the latest revelation.

"Simply everyone that has a Yahoo account should be concerned," Robert Siciliano, a US-based security analyst, told Al Jazeera. "Once a criminal hacker has access to your email, that is a portal to reset the passwords for all of your critical accounts, which that Yahoo account is associated with."

Both lapses occurred during the reign of Yahoo CEO Marissa Mayer, a once-lauded leader who found herself unable to turn around the company in the four years since her arrival. Earlier this year, Yahoo agreed to sell its digital operations to Verizon Communications for $4.8bn - a deal that may now be imperiled by the hacking revelations.

Yahoo didn't say if it believes the same hacker might have pulled off two separate attacks. The Sunnyvale, California, company blamed the late 2014 attack on a hacker affiliated with an unidentified foreign government, but said it hasn't been able to identify the source behind the 2013 intrusion.

Yahoo: Users need not worry

Yahoo has more than a billion monthly active users, although some have multiple accounts and others have none at all. An unknown number of accounts were affected by both hacks.

In both attacks, the stolen information included names, email addresses, phone numbers, birthdates and security questions and answers.

The company says it believes bank-account information and payment-card data were not affected. But hackers also apparently stole passwords in both attacks. Technically, those passwords should be secure; Yahoo said they were scrambled twice - once by encryption and once by another technique called hashing.

But hackers have become adept at cracking secured passwords by assembling huge dictionaries of similarly scrambled phrases and matching them against stolen password databases.

That could mean trouble for any users who reused their Yahoo password for other online accounts. Yahoo is requiring users to change their passwords and invalidating security questions so they can't be used to hack into accounts. (You may get a reprieve if you've changed your password and questions since September.)

Security experts said the 2013 attack was likely the work of a foreign government fishing for information about specific people. One big tell: It doesn't appear that much personal data from Yahoo accounts has been posted for sale online, meaning the hack probably wasn't the work of ordinary criminals.

That means most Yahoo users probably don't have anything to worry about, said JJ Thompson, CEO of Rook Security.





http://www.aljazeera.com/news/2016/12/yahoo-suffers-world-biggest-hack-1-billion-users-161215034225047.html

yahoo boys

What

NOTICE OF DATA BREACH

Dear xxxxxxxx,

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
 



That was the message I received from Yahoo. Hence, if you are affected, there's need for you to alter your password, security questions and answers for any other accounts on which you used the same information.