The company said it believes a state-sponsored actor was behind the data breach, meaning an individual acting on behalf of a government. The breach is said to have occurred in late 2014.
Yahoo urges users to change their password and security questions and to review their accounts for suspicious activity.
The silver lining for users is that sensitive financial data like bank account numbers and credit card data are not believed to be included in the stolen information, according to Yahoo. Yahoo is working with law enforcement to learn more about the breach.
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