Hospitals and clinics across the country were forced to turn away patients on Friday after the mass-distributed ransomware virus caused them to lose access to their computers.
'There has been one incident of the ransomware hitting a business here in Australia and there could be two other incidents where it has occurred although we are trying to confirm that, ' he said.
"It's always bad for any businesses to be a victim of crime, but as a whole of nation we can be confident so far that we have missed the worst of this", he added.
Problems with cyber security in the NHS was highlighted a year ago by Dame Fiona Caldicott, the national data guardian, who warned issues were given insufficient priority and that health bodies persisted in using obsolete computer systems, The Times reported.
The government is targetting small businesses in it's mitigation messaging which it believes are most at risk from the ransomware.
The insidious bug has crippled systems across the globe, prompting Cyber Security Minister Dan Tehan to call for urgent action from local companies.
Cyber security firms had urged all users to update Windows software last month after hackers leaked a cyber tool stolen from the US National Security Agency. Microsoft released a security update in March to protect against WannaCrypt but Windows XP was excluded from the patch. The exploit codenamed EternalBlue exploited an SMB vulnerability. One of the most notable infections took down a large portion of the United Kingdom's National Health Service.
"We back up what we put into the system every night, but Friday's information will be gone".
The trust, which runs Boston, Lincoln and Grantham hospitals, says to attend "unless patients recieve a telephone call" saying otherwise as some systems are still affected.
The National Cyber Security Centre has been coordinating the State's response to the threat from the fast-spreading malicious software and has issued a series of advisory notices to Government departments and agencies.
Rob Whiteman, CIPFA chief executive said: "The NHS ransomware attack needs to be a stark reminder for all government organisations to ensure IT security is optimal, regularly reviewed and upgraded, and given the resources to match our reliance on digital systems".