Reuters reports that all of the almost four million customers of major Australian health insurance provider Medibank had their data compromised in a ransomware attack this month. Medibank disclosed that all of its customers' personal and health claims data have been accessed by threat actors, just a day following its warning that more customers could have been affected by the cyber incident. "Our investigation has now established that this criminal has accessed all our private health insurance customers' personal data and significant amounts of their health claims data. I apologize unreservedly to our customers. This is a terrible crime this is a crime designed to cause maximum harm to the most vulnerable members of our community," said Medibank CEO David Koczkar. However, the health insurer emphasized that the ransomware attack has not resulted in any encrypted systems. "Everywhere we have identified a breach, it is now closed," said Medibank Head of Technology and Operations John Goodall.