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.

Insurance company Aflac disclosed this week that cybercriminals breached its U.S. network and may have accessed customers’ personal information, the latest in a string of cyberattacks on insurance companies announced this month.

The company confirmed today that it was breached by hackers, who may have stolen sensitive information from its millions of customers. Here’s what to know. Aflac Incorporated (NYSE: AFL) was the most recent target of a “sophisticated cybercrime group” that has led a campaign against a number of insurance companies in recent weeks,