This is a nasty one.
I’ve warned before about the scareware threat where warning boxes pop up, tell you that you’re infected with some virus, and then tell you that the quick remedy is to “click here” to fix the infection. These new perpetrators are worse…they essentially lock out your computer until you pay.
Your best friend with these little popups is the hot key combo “Alt-F4″ which will close the active window without clicking on anything.
As always…be careful while you surf…