When the FBI broke up a ring of cyber thieves based in Estonia last year, they started the clock ticking on a computer virus time bomb that will go off Monday, July 9.

The thieves were hijacking the way people's computers find website addresses, diverting them to websites where they would sell things or use other tricks to make money.

The scheme penetrated some 570 million computers worldwide, according to the FBI, and tens of thousands of computers remain infected.

The FBI went out of its way to keep people online for the last year, setting up servers that would keep people online and going to legitimate websites.

But they're about to pull the plug on that backup system, and people whose computers remain infected will find themselves in the dark Internet-wise come Monday morning.

There's a very quick and simple test to see if a computer is infected. Simply click this link to test for the DNS Malware virus.

If the background of the resulting image is green, you're safe. If not -- you need to follow the instructions to cleanse the virus off of your computer.

The FBI estimates some 64,000 computers in the United States remain infected.