I have discovered what some people might call a more "low-tech" method of prevention in cases such as this.
In most cases, the malware cannot infect a computer without some interaction on the part of the owner.
For instance - Clicking on a link, image or attachment from an unknown sender -- or trying to close or "X-OUT" of a pop-up window with a warning.
The bad guys rely on that very first moment of confusion and indecision - when you will try to click or close or delete -- or do something -- and they will use those actions as their means of gaining entry to the system.
When presented with one of those scary pop-ups, here's what I tell people to do:
Take your hand off the mouse and step away from the keyboard!
Then - the next thing to do is immediately disconnect your computer from the internet by directly pulling out the power cord of your modem. Once you see the icon informing you that you have lost your internet connection, I will also unscrew the coaxial cable - just for good measure.
Next - shut down your computer via the power button.
Yes - I know -- You might "lose some work" -- but that's a small price to pay, considering the alternatives.
Restart your computer - and spend a few minutes running a few trusted programs and opening known documents before connecting to the internet. If you still have an odd email sitting in your inbox, you can try to delete it. If you have to do that, after deleting, reboot again.
Once you have confirmed that you are in the clear, you can go ahead and re-connect your modem and go back online.
This may sound silly - but it has actually saved both my wife and myself on a couple of occasions.
Remember - In cases such as this, a moment of calm thinking can go a long way.