Microsoft Australia has warned customers that scammers were posing as local Microsoft partners offering to purge "infections" from users' computers.
The Redmond giant's chief security adviser in Australia, Stuart Strathdee, said the scam went under several names, including Support on Click, ITEZY.com and System Recure.
Websites for all of those companies falsely claimed they were Microsoft partners and misused the Microsoft logo.
Customers typically received a call from someone claiming to be working for Microsoft or "your ISP".
The phone number ID showed up as originating from Australia, although Microsoft said the caller was "from India or overseas".
"They will typically tell you that your computer has been running slowly and this is likely due to ‘infections'," Strathdee said.
"They tell you they can help you with this and direct you to a website that then allows them to take remote control of your PC (in doing this they could download spyware to your machine)
"The ‘cold caller' will then spend some time on your system trying to demonstrate where all your ‘problems' are and they will then try to sell you their ‘fixing' service and take your credit card details."
Microsoft said customers who received the calls should hang up immediately.
"If you receive an unsolicited call from someone offering assistance to fix your computer then we suggest you hang up, and not respond to any communications from these scammers," the company said.
It said it was continuing "to work with law enforcement and relevant government agencies."