Russian hackers are behind a massive cyber attack at Australia's largest health insurer, Medibank, the Australian Federal Police (AFP) said Friday.
Data stolen from Medibank began appearing on the dark web on Wednesday after the company refused to pay a ransom to the hackers.
About 9.7 million current and former Medibank customers are believed to have been affected by the October hack.
AFP commissioner Reece Kershaw told a media conference the attack was carried out by a Russian group that was "likely responsible" for other significant breaches across the world.
The group may have affiliates in other countries, Kershaw said.
"So to the criminals, we know who you are, and moreover the AFP has some significant runs on the scoreboard when it comes to bringing overseas offenders back to Australia to face the justice system."
Kershaw said he knew Australians were "angry, distressed and seeking answers" about the hack.
"This cyber attack is an unacceptable attack on Australia and it deserves a response that matches the malicious and far-reaching consequences that this crime is causing."
Medibank cief executive David Koczkar said the release of stolen data was "disgraceful" and was causing harm.
"These are real people behind this data and the misuse of their data is deplorable and may discourage them from seeking medical care," he said in a statement.
"It's obvious the criminal is enjoying the notoriety. Our single focus is the health and wellbeing and care of our customers."
Australian Prime Minister Anthony Albanese told media he was "disgusted" by the hack.
"We know where they're coming from, we know who is responsible and we say they should be held to account."
Data taken during the hack includes names, addresses, birth dates, passport numbers, phone numbers and health claims.
