The back-story is rather complicated, involving an online scam that got so big the FBI couldn't shut it down the ordinary way, and it begins about five months ago:

Last November, the FBI and other authorities were preparing to take down a hacker ring that had been running an Internet ad scam on a massive network of infected computers.

"We started to realize that we might have a little bit of a problem on our hands because ... if we just pulled the plug on their criminal infrastructure and threw everybody in jail, the victims of this were going to be without Internet service," said Tom Grasso, an FBI supervisory special agent. "The average user would open up Internet Explorer and get `page not found' and think the Internet is broken."

So the government brought in its own servers to replace the hacker servers, and no one on the user end knew the difference.

The problem: No one on the user end knew the difference.

The FBI doesn't want to act as a bunch of people's ISP forever, so now it's warning everyone with a PC to check themselves (or at least their computers) before their Internet lives get wrecked on July 9 when the FBI pulls the plug on those backup servers.

The FBI is encouraging users to visit a website run by its security partner,, that will inform them whether they're infected and explain how to fix the problem. After July 9, infected users won't be able to connect to the Internet.

Predicted first comment: "Another reason to use a Mac."