Eastern Health, the operator of four hospitals in Melbourne’s east, has been hit by a cyber attack forcing it to postpone certain elective surgeries.

In a statement, Eastern Health said the incident occurred on Tuesday night.

“Many Eastern Health IT systems have been taken off-line as a precaution while we seek to understand and rectify the situation,” it said.

“It is important to note, patient safety has not been compromised.”

The health services provider said category one elective surgeries will go ahead but it would have to postpone “less urgent” surgeries due to the cyber attack.

Eastern Health runs hospitals in Box Hill, Maroondah, Angliss, and Healesville along with health centres in the Yarra Valley and Burwood East.

While the nature of the incident is unknown, cyber security experts have suggested ransomware is a likely cause of the disruption.

And the Australian Cyber Security Centre (ACSC) recently said ransomware was the “most significant cybercrime threat to the Australian health sector”.

In early 2019, Cabrini Hospital in Melbourne was locked out of its systems during a ransomware attack.

Jacqueline Jayne, a security awareness advocate with KnowBe4, said hospitals were a veritable treasure trove of valuable data for cyber criminals.

"Hospitals are a very attractive target for cybercriminals due to the nature of the information they hold on their patients – information that, once obtained, can be used for identity theft and sold multiple times on the dark web,” she said.

“This is not only health-related data, as the addition of personally identifiable information (PII) is also there for the taking.”

Rick McElroy, head cyber strategist for VMware Carbon Black, said his team has observed the kinds of dark web activity aimed at buying and selling patient data.

“On the dark web, we have found everything from protected health information to COVID-19 test results as well as opportunities to join ransomware affiliate groups, making it easily accessible to millions of cybercriminals who previously didn’t have the tools to carry out these attacks,” he said.

Health service providers had the largest number of data breach notifications to the Office of the Australian Information Commissioner (OAIC) last year.

But while the industry was heavily targeted online, the health sector was one of the best for identifying data breaches in a short period of time.