The attack came to light early yesterday, hitting a Miami-based IT company, Kaseya, and infiltrating companies using that firm's software.
Daniel Ayers said this type of "supply chain" attack is critical and there are variety of IT service providers in New Zealand that use Kaseya.
There's been information released on the web that there are people affected in New Zealand. a number of the anti-virus providers have released information that they need seen detections in New Zealand.
He said the timing of the attack means some companies might not discover they're affected until they begin work tomorrow morning.
The cyber-security watchdog CertNZ is advising organisations using Kaseya to pack up those servers.
Kaseya provides IT management software for Managed Service Providers (MSPs) and little to mid-sized businesses (SMBs) - linking clients and partners in New Zealand.
Kaseya has previously publicised its links to New Zealand-based CodeBlue and other Australasian IT companies, including BigAir, Datacom, eNerds, Leap Consulting, Surety IT and Ricoh Australia.
President Joe Biden has directed US intelligence agencies to research who was behind the attack that also hit many American businesses.
As well, 500 Coop supermarket stores in Sweden are forced to shut .
Coop Sweden said it closed quite half its 800 stores on Friday after point-of-sale tills and self-service checkouts stopped working.
Security firm Huntress said it believed the Russia-linked REvil ransomware gang was responsible for the newest ransomware outbreak. Last month, the FBI blamed an equivalent group for paralysing packer JBS.
In a statement, the US Cybersecurity and Infrastructure Security Agency said it had been "taking action to know and address the recent supply-chain ransomware attack" against Kaseya's VSA product.
US and British authorities said Russian spies accused of interfering within the 2016 US presidential election have spent much of the past two years abusing virtual private networks (VPNs) to focus on many organisations worldwide.
Russia's embassy in Washington has denied that charge.