People around the world are urged to use caution when using their computers starting Monday due to a widespread virus that could shut down a quarter of a million personal computers.
The cyber-scam, called The DNSChanger, has been found in 250,000 computers worldwide.
At least 50,000 computers in the United States could go dark if users don't apply a software patch created to fix the problem.
The world discovered the virus last November when the FBI busted a ring of Estonians whose software infected machines, without users knowing it, by re-routing them to fake sites.
Steven Bellovin with Department of Computer Science at Columbia University explained, "Instead of going to your bank, you go to some Web site that they control and they can go capture your bank password."
The FBI said four million computers were infected in 100 countries. They built a temporary backup system to keep people online, but planned to shut the system down Sunday night.
Bellovin said, "The government, they're trying to be helpful, the interesting thing here is that this was indirectly relying on a piece of infrastructure that the bad guys controlled."
The site has been up for eight months, but at 11 p.m. CT Sunday, experts terminated the operation and now they're urging people to look for suspicious activity within their computers and in any accounts.
For more information on how to check to see if your computer is infected, click here.
If your computer is infected, click here to learn how to fix it.