After several months of news reports and speculation, Yahoo on Sept. 22 confirmed that it was the victim of a nation-state cyber-attack that resulted in one of the largest data breaches ever. Yahoo said at least 500 million user accounts were stolen in the attack. While Yahoo is working with law enforcement to try to trace the attackers, Yahoo users—many of whom have been using the company’s web applications, particularly email, for 20 years—are now left to pick up the pieces. Yahoo has asked users to reset their passwords and the company said in a statement that it will inform those who might have been directly affected. But that’s the least of users’ concerns. Armed with Yahoo credentials, it’s possible for the hacker to exploit other, unaffiliated user accounts, especially those of Yahoo customers who use duplicate passwords for multiple websites and online services. It’s also possible that the hackers already are attacking Yahoo’s computers and mobile devices without them even knowing it. To help users who may have been affected by this or similar cyber-attacks and data breaches, this slide show provides a brief guide on what users should do in response to the massive breach. Following these…