A warning has been issued about a rising risk of hackers gaining control of home computers.
Microsoft's latest security report shows a sharp rise in security breaches in New Zealand.
Microsoft security figures for October 2008 show notifications of breaches rose from 3.8 per 1000 computer users, to six per 1000 - an increase of more than 40%.
Microsoft security expert George Stathakopolous says consumers face a constant threat from rogue software.
He says risks include buying software on line, which may be embedded with malicious software.
Clients can be lured into giving credit card numbers, or may reveal clues to passwords via social networking sites such as Facebook.
Mr Stathakopolous says computer users must be vigilant and install good security, because once rogue software is inside a computer the machine is controlled by a hacker rather than its owner.
Overall, New Zealand is ranked as the world's sixth-cleanest computer environment.