Though the US government limited the damage from the Alureon DNS changer malware attack last November by setting up temporary servers to fix infected machines, those servers are due to be shut down on Monday.
The announcement has led to widespread warnings of an impending internet blackout, as security firm Deteque alleges that 245,000 computers worldwide are still infected with the virus.
The FBI's servers were set up to replace the DNS-redirected destinations of Alureon, sending infected machines to a page that would check for the virus and fix it, instead of displaying the phishing and scamming content of Alureon's servers.
Deactivating the servers that are still supporting these infected machines could conceivably see them try to reconnect to Alureon's servers which, though the rogue servers were taken down last year, could instead mean that up to a quarter of a million computers will be unable to connect to the internet at all.
The malware is not difficult to remove, with a wide variety of tools readily available.
Dan Brown, director of security research at threat protection firm Bit9, said: "Security was not paid a great deal of attention while the internet was first forming. Now, years later, we're stuck with the bill. It's long been known what the fix for this particular problem is DNSSEC, but like kids eating vegetables, it's something we put off as long as possible.
"Consumers and corporations that follow good security hygiene aren't affected by this malware," Brown continued, before adding that users can also limit future damage by ensuring a computer's "Guest" account is used for general surfing, "so that any potential malware infections are confined and won't have the ability to compromise individuals' personal and sensitive data."
Brown also suggested that companies should consider the use of application control technology which "often succeeds where traditional antivirus fails in preventing novel malware such as DNS Changer".