Hackers who seized thousands of Aussies' private data during huge Medibank hack demand a RANSOM – as ministers warn the cyber attack is 'significant'

• Australian private health insurer Medibank has been the victim of a cyberattack
• The company has the personal information of more than 3.9millilon customers
• CEO David Koczkar said insurer was trying to understand extent of the breach 
• A group claiming to be behind the attack contacted Medibank on Wednesday  

By Brett Lackey For Daily Mail Australia

Hackers who claim to be behind a cyber attack on one of Australia's largest health insurers, Medibank Private, have threatened to release customers' personal information.

Medibank said in a statement on Wednesday that a group had contacted them wanting to enter ransom negotiations over the allegedly stolen data.

'This is a new development and Medibank understands this news will cause concerns for customers and the protection of their data remains our priority,' the company said.

'We are working urgently to establish if the claim is true, although based on our ongoing forensic investigation we are treating the matter seriously.'

Messages in broken English allegedly from the hacking group claim 200 gigabytes of sensitive information, including health records, was stolen from Medibank, the Sydney Morning Herald reported.

The group said as a 'warning shot' it would contact the insurer's 1,000 most prominent customers including 'politicians, actors and activists' using their own personal information.

Private health insurer Medibank revealed last week it was the victim of a cyberattack and now the hacking group has made demands