I use NIS 2010. I was surfing when suddenly a screen pops up saying I am infected with a virus and I should download Antivirus package, then a screen shows a fake hard drive image as if my own and warning that all my files are about to be deleted. I do not recall the exact name of the Antivirus program I was supposed to download.
I powered off immediately. When I rebooted all seemed ok and a scan with Malwarebytes showed nothing. Norton log showed no threats, and no warnings from Norton ever occured.
I wonder what happened here, and why powering off seemed to prevent getting infected, and why Norton noted nothing unusual nor did it block the threat.
That was an attempt of a rogue antivirus program trying to entice you to click on something. You did the right thing by not clicking on anything and powering off right away. I assume you did a full scan with Malwarebytes after you updated it.
I think it would take longer to do that via task manager. The idea is to power down your computer as fast as you can before any damage can be done. After you reboot, then do a complete scan with malwarebytes and your Norton product to make sure you are clean.