Whanganui District Health Board has been targeted by hackers who infected its computers with a "ransomware" attack.
The virus, known as "Locky", has spread to hundreds of thousands of computers around the world since first appearing on Monday.
Ransomware attacks restrict people from accessing files on computers until a ransom is paid to the hacker.
Forbes reported Locky was transmitted to computers via a Word document and encrypts files stored on the computer's network until a ransom of Bitcoin is paid. Researchers told Forbes Locky was being sent out by Russia's biggest cyber-criminal gang.
Whanganui District Health Board's information and communications technology manager Barry Morris said the threat from Locky had been contained and no ransom was paid to the hackers.