SAN FRANCISCO — Yahoo says the personal information in 500 million accounts was stolen in a massive security breakdown.

The breach, disclosed Thursday, marks the latest setback for the beleaguered internet company and dates back to late 2014.

The stolen data includes users’ names, email addresses, telephone numbers, dates of birth, hashed passwords and security questions for verifying an accountholder’s identity.

Yahoo is blaming the hack on a “state-sponsored actor.”

Yahoo is recommending that users change their passwords if they haven’t done so since 2014.