Information tied to customers’ insurance claims and personal data may also have been breached in the cyberattack, Aflac said. “We regret that this incident occurred,” Aflac said. “We will be working to keep our stakeholders informed as we learn more and continue investigating the incident.”

Aflac Inc. said a recent cybersecurity breach could have given intruders unauthorized access to customers’ personal information, including Social Security numbers, as well as health and claims data.

It’s the largest insurance company yet to fall victim to a major hacking, with tens of millions of customers and a $55 billion market cap.