As a top Australian spy agency continues to investigate a cyber attack on two regional Victorian hospital networks, almost 30 patients have had surgeries cancelled.
Barwon Health chief executive Frances Diver said 27 elective surgery cases had been cancelled over the past two days, while 140 procedures went ahead as planned.
"Yesterday we undertook about 50 elective surgery cases and we cancelled about 16," she told 3AW on Wednesday.
About 11 cases were cancelled on Wednesday.
"We are actually able to provide most of our services.
"It's just about individual clinicians going through each of the cases and determining if they can proceed with the surgery with the information available to them in theatre."
Hospitals linked to the Gippsland Health Alliance and South West Alliance of Rural Health were among those targeted by ransomware on Monday.
Authorities denied personal patient information was accessed.
The centres isolated and disconnected a number of systems to quarantine the infection, as federal and Victorian authorities investigate.
The Australian Cyber Security Centre - part of the secretive Signals Directorate - alongside Victorian and federal police are probing the attack, and on Wednesday issued a general statement about hacking.
"Malicious cyber activity against Australia's national and economic interests is increasing in frequency, scale, sophistication and impact," the statement said.
"No internet-connected network is 100 per cent secure, and no single sector is immune."
An auditor-general report released in May warned Victorian hospitals - including those under Barwon Health - that cybersecurity needed improvement.
It is not clear how many of the report's 14 recommendations Barwon Health has implemented.
David Cullen, principal advisor to the Victorian government on cyber incidents, could not say how long it would take to get the systems running again or why the two hospital networks had been targeted.
But he admitted it would be "a long, complex and protracted forensic investigation".
Australian Associated Press