Fortunately I was alert enough to avoid being a victim.
I contacted Microsoft and "Scamwatch" and researched on the internet...
The scam dates back to 2009 as per police media report http://www.police.qld.gov.au/News+and+Alerts/Media+Releases/2009/04/New+scam+targets+computer+users.htm
They "cold call" claiming they are working with Microsoft (or your internet service provider) to remove virus infection due to a software warranty running out. Even if you claim to have antivirus software, they lead you to an error log to prove that errors are happening and that they can fix this.
DO NOT let them have remote access to you computers!!!
Anyone wishing to report a fraud matter or provide information to police is asked to contact Crime Stoppers on 1800 333 000.
