At least half a billion Yahoo accounts have been affected in one of the biggest data breaches in history. Names, email addresses, telephone numbers and hashed passwords may have been stolen. Yahoo has blamed the attack on a “state-sponsored actor,” but it’s far from clear who hacked the internet company and how the culprits pulled off the attack. The stolen data from Yahoo can be used in other ways to attack victims, security experts say. Security experts advise affected users to change their passwords and security questions.”]