MADISON, Wis. -

A worldwide computer virus has been stopped, but if people don't diagnose and fix their home computer it could bring their web browsing to a halt.

The virus itself is under control after the FBI said it arrested Estonian hackers who had taken over some 570,000 computers trying to get at personal information. Investigators have been maintaining the servers while trying to get the involved PCs fixed, but that's the challenge. It's estimated thousands of people in the U.S. still have the virus and don't know it.

"Really the only indication you might have is (your computer) might be slower, your connection might be slower," said Mike Masino, a network security expert at Madison College. "If you've got a really fast machine and a fast connection you really might not even notice this is going on."

Some PC users at Madison College said they hadn't heard of the virus or even scanned for viruses lately.

"I don't think about it at all," said Luke Kelley, of Sauk City.

"I don't know if I'd have the virus or not," said Evan Everett, of Jefferson. "It would be interesting to see what happens when the time comes.

Masino said the good news is there is a website that can help, www.dcwg.org.

"They've set it up so it will detect whether or not your machine is infected with it," Masino said. "It's really simple; green or red warning screens will show you yes or no if it is infected. There are also good tips on how to fix it if you are infected."

The FBI said it plans to shut down servers in July, and if a computer hasn't been fixed, it will lose all access to the Internet. Masino said all is still not lost, as Internet service providers should be able to help their customers.

"Don't panic," Masino said. "They'll be able to fix you up and get you back up if your Internet goes down in July."

Users did have some trouble accessing the website Monday afternoon, and Masino said service may be spotty because of high traffic.

As to how people got infected in the first place, Masino said experts are not sure how the virus was packaged but it's likely that users clicked on and downloaded something that allowed hackers to access their computers.