Back in October 2010 Kinetics warned of a cold calling scam where the caller tells you that you have a PC issue and offers to help.

http://www.kinetics.co.nz/newssite/Pages/2010PhishingExperience.aspx. 

Recently this scam has received a lot more publicity.  The number of instances does seem to be increasing; yesterday both a client and my unlisted home phone received this call.  The caller may claim to be from Microsoft and is warning you that your PC has been hacked, infected or is at risk.  They will then offer to resolve the problem for you.    They will try to talk you into installing software which will steal your credit card number.

TVNZ’s Fair Go has now reported this as an increasing risk.  You can read more on the Fair Go segment at http://tvnz.co.nz/fair-go/june-1-4202937 or view it at http://tvnz.co.nz/fair-go/pc-virus-cold-callers-6-23-video-4203083