Which yahoo accounts were hacked

Yahoo has 1 billion monthly active users on its services overall and just million monthly active users for its Yahoo Mail service, according to figures the company gave CNET in June. So check the email affiliated with your Yahoo account if you haven't already.

Yahoo has started sending out notifications to users, and you should be receiving one at that account if you were affected by the data breach.

If you haven't changed your password in a few years, do it -- now. The company says the passwords that hackers stole were encrypted -- scrambled up with a tool called bcrypt. This kind of encryption can potentially be broken with enough persistence, said Brett McDowell, executive director of the FIDO Alliance, a nonprofit group that vets login systems.

That's especially true "when the attacker can make relatively accurate guesses at what the password might be," McDowell said. It's a common habit. Use the same password for lots of different accounts. If this breach has anything to teach you, it's that this is a terrible idea.

In order to ensure that you also get those replies, the attacker can set up a forwarding rule in their own email account and automatically forward those replies to your address. Large data breaches are typically followed by email phishing attempts, as cybercriminals try to take advantage of the public interest in such incidents.

Be on the lookout for such emails and make sure that any instructions you decide to follow in response to a security incident came from the affected service provider or a trusted source. Official Yahoo emails are easily recognizable in the Yahoo Mail interface because they are marked with a purple Y icon. In the future, be selective in what personal information you choose to share and which websites you choose to share it with, even when those websites are legitimate. These details can be used to impersonate you or to authenticate you on other websites.

Whether or not people use Yahoo services , they should always practice proper computer hygiene, experts say, such as not reusing passwords and implementing two-factor authentication on all their accounts.

Timeline: The rise and fall of Yahoo. How to protect yourself from hackers. CNNMoney Sponsors. SmartAsset Paid Partner. These are your 3 financial advisors near you This site finds and compares 3 financial advisors in your area Check this off your list before retirement: talk to an advisor Answer these questions to find the right financial advisor for you Find CFPs in your area in 5 minutes. The closing of the Verizon deal, which was first announced in July, had been delayed as the companies assessed the fallout from two data breaches that Yahoo disclosed last year.

A Yahoo official emphasized Tuesday that the 3 billion figure included many accounts that were opened but that were never, or only briefly, used. The company said it was sending email notifications to additional affected user accounts. The new revelation follows months of scrutiny by Yahoo, Verizon, cybersecurity firms and law enforcement that failed to identify the full scope of the hack. The investigation underscores how difficult it was for companies to get ahead of hackers, even when they know their networks had been compromised, said David Kennedy, chief executive of cybersecurity firm TrustedSEC LLC.

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