On July 9, thousands of Canadians run the risk of losing access to the Internet because of a years-old virus created in Estonia.

As the CBC reported, on Monday the FBI will be turning off temporary servers that have been helping affected computers to get rid of the DNSChanger virus and return to accessing the Internet normally. Now, those who haven't taken action to fix their computers will find themselves unable to visit any websites when those servers are turned off.

What's happening

In brief, a group of six Estonians created the DNSChanger virus as a way to reroute Internet users' traffic to sites where the group could profit from ad clicks. The FBI shut them down as part of the two-year Operation Ghost Click.

[ More The Right Click: New Trojan scam extorts money from Canadians ]

To allow those who were affected by DNSChanger continue to access the Internet while they removed the virus from their computers, the FBI set up a group of temporary servers to serve DNS addresses. As of Monday, the contract with the company running those servers expires, which means anyone who still has the virus on a computer will no longer be able to access the DNS servers. No DNS server, no Internet. This FAQ explains in more detail all of this in layman's terms.

The one thing you need to do to make sure you're safe

To check if your computer is at risk, all you have to do is visit http://www.dns-ok.ca. Scroll to the bottom of the page and agree to the terms and conditions in your language of choice. The next page will either display two green banners if your computer is clear, or two red banners if your computer is infected.

What to do if your computer is infected

If you are one of the unlucky ones with a red banner, don't worry, you aren't alone: approximately 7,000 computers in Canada are still harbouring the virus. There was also an estimated 12 per cent of Fortune 500 companies that still had the virus on some of their computers as of two weeks ago.

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DCWG has lots of information on the DNSChanger malware, including how to remove it. As with most infections, make sure your data is backed up, then take your computer to a computer store or to a computer expert you trust to perform the removal of the malware. The free tools listed on the DCWG site can be used to remove the malicious files from your computer.

To prevent an attack like this from affecting your computer again in the future, CNET recommends that all computers — Mac, PC, iOS or Android — should have some kind of security software installed. It is also recommended that you only enter personal and identifying information on sites that you trust. Verify the site's URL before entering anything.