A computer science expert hopes Waikato DHB's cyber security woes are over by tomorrow

The District Health Board's IT service is down after a major cyber incident, affecting all clinical services and forcing patient appointments to be cancelled.

AUT professor Dave Parry says it appears to be a ransomware attack.

He says that's where attackers encrypt files and say they'll give passwords in return for payment.

But Parry says New Zealand doesn't pay ransomware.

He says the DHB can restore things from backups - which takes time and has to be done systematically - but he would be surprised if it takes more than a day.