The more common current scam is the link on a web site that warns you that your computer is "infected." Since a "click" on the link is effectively a permission for them to send you something, your computer thinks you've given permission for them to download something that is an infection, after which they urge you to buy their program to "fix it."

In the US, my response to such phone calls is

"This number is listed with the Federal Do Not Call Registry, and I have no business relationship with you that permits this call. The fine is $10,000 per call, but if you'll send me half within 24 hours I'll hold off on filing a report."

I then promptly hang up in an attempt to be rude - although I've never been able to beat one of these callers at disconnecting. They're usually gone when I get to "Do Not Call Registry."

John