Prepare for a nasty shock on April Fool's day, security experts have warned.
That's because the Conficker worm, otherwise known as Downadup, is set to activate on 1 April.
A variant of the worm known as Conficker C is the focus of security experts' attention and is thought to have infected millions of PCs worldwide without the knowledge of their owners.
What is not clear is what exactly will happen.
Predictions range from a massive DDoS (distributed denial-of-service) attack on a major website or social network to a widespread wiping of hard disks on the PCs it has infected.
However, it could be far less serious.
"Speculation continues on whether the payload will be one big April Fool's joke, or the equivalent of a cyber Pearl Harbor," said Symantec's Eric Chien.
"While we can't predict the future with certainty, we can look at the motivations of past Downadup variants to postulate that the payload will likely be something between the two extremes," Chien continued.
According to Symantec, the amount of media attention Conficker C is receiving could affect what happens on 1 April.
"Considering the amount of eyes now watching Downadup's every move, we also can't underestimate the chance that the authors may veer from their original motives," Chien said.
If you suspect you have been infected by the Conficker worm, you should make sure your anti-virus application is up to date, restart your PC in Safe Mode, and run a full system scan.
Trend Micro has also come up with a free tool to remove Conficker available to anyone, not just Trend Micro customers.
