Your web connection may not last into Monday

(CBS News) NEW YORK - The FBI is out with what amounts to a Doomsday warning for Internet users.

On Monday at 12:01 a.m. Eastern time, a malicious virus hiding in hundreds of thousands of home and business computers may make them lose their Web connections.

It's known as a "DNS changer" virus and has "been around for a long time," Reuters Mediafile columnist John C. Abell explained to "CBS This Morning: Saturday" co-hosts Anthony Mason and Rebecca Jarvis. He said last year the FBI and other law enforcement organizations made arrests in Estonia relating to the "DNS changer" virus.

"What they were doing was changing where you went when you typed in a web address," Abell said. "So if you typed in cbs.com, you wouldn't show up at the real cbs.com - you'd show up someplace else."

To find out if your computer has the virus, simply click here before Monday.

"You'll get a nice graphic that's red or green," Abell said. "Green means you're fine. Red means you need to download some software. It will take care of the virus that's there. It will reset the DNS numbers and you'll be fine."

It's estimated that several hundred thousand computers have the virus.

"This has been known for quite some time," Abell continued. "There've been all kinds of warnings: We sent the car, we sent the boat, we sent the helicopter. Now it's time to do something.

"But the worst-case scenario here is that you won't be able to do anything (on the web) until you do the fix. And the fix is really quite simple.

"If you don't know how to do it, get a teenager," Abell added.

To protect your computer from viruses, Abell said, always use a firewall and anti-virus software, especially for Windows machines, which are "very very vulnerable. This (particular virus) affects Macs AND Windows machines. Have your anti-virus software update repeatedly. One of the things this virus did was it stopped the updates, which meant that, even though you were just not getting to the right website, it meant you were vulnerable to other viruses. You have to have anti-virus software and a firewall, period. Then you're usually OK."