Computer users running some Microsoft systems are being warned to update their security protection.
The 'WannaCry' ransomware attack appears to have struck New Zealand and the Government's cyber security agency is urging people to be extra vigilant.
CERT NZ operations manager Declan Ingram said people shouldn't click on suspicious links or attachments.
"It takes advantage of a software defect in the Microsoft Windows system that allows it to take over peoples' computers and encrypt their files."
The ransomware threatens to destroy people's computer files if they don't pay US$300.
The cyber attack has disrupted operations at car factories, hospitals, shops and schools.
It is also said to have locked up more than 200,000 computers in more than 150 countries.
Microsoft has pinned blame on the US government for not disclosing more software vulnerabilities.
Cyber security experts believe the spread of the worm has slowed, but respite may be brief amid fears new versions of the worm will strike.
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