They're calling it "Doomsday" and, for some, it will be on July 9, when hundreds of thousands of victims face the possibility of being unable to connect to the Internet.
Ironically, that's because of a decision by the FBI to switch off a special program that has been keeping more than half a million infected PCs online since last year.
Victims likely don't know their machine has been infected and, if they don't check, come July 9 the Internet will just plain disappear for them.
Their computers are infected with a piece of malware known as "DNSChanger" that connected them to servers running a now-defunct online advertising scam.
These servers were in turn connected to the Internet, so victims wouldn't necessarily realize what happened, apart from their PCs maybe slowing down a little.
The malware also disabled virus-checker updates so even people who had Internet security software couldn't detect it.
Then, when users tried to access certain websites or run a search, they were directed to bogus web pages full of ads, which netted the crooks an estimated $14 million.
We don't need to go into the technical details of how this was done, but when police seized the scammers' computers they were left with a problem -- those half million victims were now reliant on them to connect to the Internet.
So the FBI replaced them with "clean" machines that would keep the Internet link open -- without the scam running.
Victim computers, of course, still have the virus but without anything nasty happening.
But when the FBI switches off its servers, those machines will lose their online connection and won't know where to find the Internet!
Are you one of the victims?
Fortunately, there's a relatively easy way to check and to put things right thanks to a website that can detect infected machines and provide instructions on how to set things right again.
Simply go to http://clicks.aweber.com/y/ct/?l=OT3bW&m=JKfg1H6IgGtWfo&b=PQ57aTASMJIwjuuvKXGVxw -- and you will either get a green (for "clear") or red (for "infected") page.
The check does not download any software onto your PC. Nor does it run a scan. It just checks where your computer is looking for the Internet.
If you're in the clear, that's all you need do.
If it says your computer is infected, go to http://clicks.aweber.com/y/ct/?l=OT3bW&m=JKfg1H6IgGtWfo&b=O6q1sgmbcrXVvzssQOBjBg for free removal tools and more information on what to do next.
If you don't want to click directly on any of these links, key in and go to dcwg.org, a site specially set up by the FBI and Internet security specialists to deal with this online advertising scam.
Good luck!