Insurance giant Aflac identified “suspicious activity” in its U.S. network, which initiated its cybersecurity protocols. Aflac said it was able to stop the attack within hours, and its systems were not affected by ransomware.

The insurer said it’s in the early stages of a review of the incident, and so far is unable to determine the total number of affected individuals.

Aflac confirms June 12 cyberattack that exposed Social Security numbers and personal data in a wave targeting US insurers.