June 20 (UPI) -- Insurer Aflac said Friday customer health data and Social Security numbers were hacked, but that it stopped the cyber intrusion within hours and the attack did not include ransomware.

Aflac is a U.S.-based company best known for its supplemental policies that help cover expenses that major medical insurance doesn't. It serves some 50 million people worldwide, largely in the United State and Japan.

Aflac said the impacted files include "claims information, health information, Social Security numbers and/or other personal information, related to customers, beneficiaries, employees, agents and other individuals in our U.S. business."

"This attack, like many insurance companies are currently experiencing, was caused by a sophisticated cybercrime group," Aflac said. "This was part of a cybercrime campaign against the insurance industry."

Aflac said it has engaged third-party cybersecurity experts to help respond to the attack.