The conficker computer virus is set to activate worldwide on Wednesday, but opinions are divided over the threat the worm poses.
The virus has infected an estimated 10 to 15 million computers.
Security experts say 1 April has been coded into the virus but are unsure what will actually happen.
IBM security expert John Martin says the virus may cause a great deal of disruption and potentially cost New Zealand businesses and organisations millions of dollars to clean up.
A task force assembled by Microsoft has been working to stamp out the worm, and the American software giant has placed a bounty of $US250,000 on the heads of those responsible for the threat.
The worm, a self-replicating program, takes advantage of networks or computers that have not kept up to date with security patches for Windows RPC Server Service.
It can infect machines from the internet or by hiding on USB memory sticks carrying data from one computer to another. Once in a computer it digs deep, setting up defences that make it hard to extract.
Computer users are advised to stay current on anti-virus tools and Windows updates, and to protect computers and files with strong passwords.
Conficker is programmed to reach out to 250 websites daily to download commands from its masters.