DENVER (CBS4) Hundreds of thousands of computers could be infected with a virus, and the owners don’t even know it. The FBI is warning to check your computer now before it becomes a problem later.

The FBI discovered a breach on about 560,000 computers. Criminals changed the domain name systems, or DNS’s, on victims’ computers to redirect unsuspecting users to fraudulent websites. The victims didn’t know their Internet browsing was being manipulated.

If the rogue servers were disconnected, many people would have lost internet access. So the FBI replaced the bad equipment with clean servers to keep unsuspecting users connected to the Internet. The new equipment was always meant to be a temporary solution, and now the FBI is preparing to shut down the system in July.

That means that every computer user needs to check their computer and router to see if their equipment is infected. Here’s a step-by-step guide of what to do:

— Go to

— On the homepage, click on the red box where is says “DNS Malware – Is Your Computer Infected”

— Scroll down to the second bullet point, click where it says “Check Your Computer’s DNS Settings”

— Then click on first link in the table, next to the word “English”

— That will check your computer and router for the virus

If you get a big green box, your computer and router are likely in the clear. If the box is red, it indicates that either your router or your computer are infected.

The next thing you’d want to do is run security software to clean your equipment. Steve Utke of Surge Computers of Highlands Ranch recommends F-Secure Easy Clean or Malwarebytes, which are both free.

“But you’re not changing your DNS’s back to what they originally should be,” Utke told CBS4.

“And how do you do that?” asked 4 On Your Side Consumer Investigator Jodi Brooks.

“That would require an IT person to get in there,” Utke replied.

Getting those DNS’s corrected could cost as much as a few hundred dollars. The FBI encourages everyone to take security seriously. The Denver Division issued this statement:

“The FBI Denver Division wants to remind all Internet users that you must be diligent in protecting your personal computing devices to include laptops, tablets, and smart phone devices from these types of aggressive intrusions.”

RELATED: More Reports By 4 On Your Side Consumer Investigator Jodi Brooks

– Written for the Web by CBS4 Special Projects Producer Libby Smith