The data was labelled STD, suggesting it related to treatment for sexually transmitted diseases, but in fact it related to clients with chronic conditions such as heart disease, diabetes, anaemia and asthma.

The dark web forum hosting the hacker’s blog – which they have used to release customer data – has been offline since yesterday.

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Medibank is not the only organisation to be hit by hackers recently.

Engineering group Aurecon is still suffering the effects of a cyberattack last month.

The Australian company, which has more than 7500 employees globally, would not say if it had been contacted by hackers for a ransom. It declined to give an update on any continuing impact on its business and referred to a statement earlier this month.

“The incident response included disabling access to Aurecon’s online platforms,” it said at the time. “As part of our ongoing response to this incident we can expect some necessary but unavoidable disruption.”

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It said that an investigation was seeking to establish the level of any impact on the company’s systems.

“We understand the urgency of this matter and will continue to keep our clients, government agencies and staff informed of any new information.”

This week, children’s charity The Smith Family confirmed it was hit by a cyberattack with hackers accessing its donors’ confidential information including credit card details.

The charity, which helps to educate children in need, has not yet said how many donors have been affected.

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Medibank has said that credit card details of its customers were not accessed as part of the attack last month, and the identity data stolen by the hackers is not sufficient to enable identity and financial fraud.

Federal Police commissioner Reece Kershaw this month named Russia as the home of the Medibank hackers as experts warned Australians to expect a wave of financially motivated cybercrime from the country.