All computers that are still using the temporary DNS severs will be blocked from the internet on July 9 until their computers are cleared of the virus.

Last year, the FBI apprehended six Estonians who had managed to organise a complicated system of fake DNS servers.

The malware would then redirect computers websites hackers had created where they were sold nearly around $14m in advertisements.

The hackers had already successfully downloaded the malware onto more than 500,000 computers while disabling virus updates. Computers could only receive internet access through these servers by the virus, DNSChanger.

When the group was dissolved last year, the FBI set up temporary clean servers in place of the corrupted ones so the computers infected with DNSChanger would not be suddenly cut off from the internet.

Many users did not and still do not have any knowledge they were infected with the virus in the first place.

The FBI servers were meant to become inactive in March this year but a court ruling extended the shut off date until July 9, 2012.

When the servers are shut off anyone who is still infected with the malware will immediately lose internet access. The DNS Changer Working Group estimates that nearly 350,000 computers are still infected.

The FBI estimates there are still around 360,000 infected computers in nearly a dozen countries.

Google is warning users who when using its search tools are detected being redirecting to DNSChanger temporary domains.

Google search users will see a warning which states, "Your computer appears to be infected," followed by a link offering advice.

According to security firm, Tacoma, nearly 50% of all Fortune 500 companies owned computers infected by the virus.

The Better Business Bureau is encouraging businesses and consumers to run a quick test to see if their computers are infected by using the FBI’s DNS Changer working group.

"Everyone should check to see if their computer is infected," urged Katherine Hutt, spokesperson for the Council of Better Business Bureaus. "It takes less than a minute to check and, if your equipment is clean, there is nothing more you need to do. If your computer is infected, the DNS Changer Working Group recommends the necessary steps to save your computer. But this must be done by July 9th or you could lose internet access."

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