"Internet doomsday" July 9, claims FBI DNS Changer was a virus run by an Estonian crime ring until authorities and the American FBI broke it up in November. At its peak it infected more than 500,000 PCs and Macs. The virus, first used in 2007, hijacked users" computers without their knowledge to generate fraudulent clicks on adverts. Although its only obvious effects were to slightly slow internet connections and to disable antivirus software, it also redirected computers to the fraudsters" servers. Turning that server off would have left users without any web access, so the FBI temporarily replaced it with a site to check whether visiting computers had the virus. The "DNS Checker Page" allows users to see if they have the virus and to remove it, and has been largely responsible for the fall in the virus's prevalence. Now the Bureau wants to turn off the server because it is costing tens of thousands of dollars to operate each month. It has announced that on July 9 it will pull the plug, potentially leaving the 350,000 computers that are still infected, 20,000 of which are in the UK and 85,000 in America, without access to the web. "If we just pulled the plug on their criminal infrastructure, the victims of this were going to be without internet service," FBI supervisory special agent Tom Grasso told Fox News. It is estimated that the criminals made £9.1 million from the scam.