The cyber-attack that's crippling Waikato District Health Board services could go on for days.

The DHB's entire IT service was brought down by hackers yesterday morning, crashing phone lines, email and computers.

All clinical services at Waikato, Thames, Tokoroa, Te Kuiti and Taumarunui hospitals are affected to varying degrees.

Elective surgeries have been postponed and patient notes can't be accessed.

It's similar to an attack on Ireland's Department of Health last week by a group named Conti.

Ireland was hit with a demand for 20-million US Dollars to get their IT system back and the problem is ongoing.

AUT's Professor Dave Parry for the Department of Computer Science told Kerre McIvor when something like this happens, it helps better prepare defence against future attacks.

"The one good thing is, that every time there is a successful attack, then the agencies and the organisations that share information about defence learn more about how that's being attacked and will fix that particular problem, and often look to see potential similar problems as well and close those off before they happen."

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