Internet security experts are warning that hundreds of thousands of internet users, whose computers were infected with a malware in 2011, might face an internet blackout on Monday.

The DNS Changer malware is at the heart of hacking scam, which was scrapped by the authorities in the US in November, 2011. However, experts say that only a small number of users are at the risk of an internet blockage.

It is believed that the risk posed by DNS Changer malware is much smaller than that from other prevalent viruses such as Zeus and SpyEye that affect millions of computers around the world. Estimates show that 245,000 computers worldwide are still affected by DNS Changer and other linked virus softwares.

The DNS Changer malware was designed to redirect Internet traffic through rogue DNS servers operated by illegal entities, US investigators had found. The US authorities bused the spamming network but kept the servers running while victim’s computers were repaired, as per the instructions of a federal judge in New York.

The US authorities will shut down the temporary servers on Monday and as a result the users, whose computers have not been fixed, might not be able to access the internet on Monday. A working group set up by experts believe that more than 300,000 computers were still infected by the virus as on June 11 with the largest number of the users in the United States at 69,000, followed by other countries including Italy, Germany, India, Britain, Canada, France and Australia.