A cyber Trojan worm is expected to hit millions of computers on April 1, but whether it will unleash a harmless April Fool's joke or a dastardly criminal plot, no one knows.

The Canadian Internet Registration Authority (CIRA) has issued a warning about the latest version of the Conficker worm, which could potentially have infected any computers running a Microsoft operating system.

CIRA, which manages Canada's dot-ca (.ca) domain name registry, says that the worm will force infected computers to connect randomly to about 50,000 web URLs a day beginning April 1.

But what could happen when those computers reach those websites is anyone's guess. Files on the websites could instruct the worm to do anything from steal passwords or banking information, to delete a person's hard drive to simply sending spam messages.

As CTV's technology expert Kris Abel explains, computer researchers made a breakthrough this week that will allow network administrators the ability to remotely identify an infected computer.

• Kris Abel: Network admin tool for Conficker virus

Experts say that anywhere from three to 12 million computers may be infected worldwide.

Most users with up-to-date anti-virus software should be fine however, as the biggest threat is towards computers, particular on large networks, that have been inactive for the last six months or so.

Microsoft has put a $250,000 bounty out to catch the cyber criminal, but so far no on has been caught.

Christopher Davis, the CEO of Defence Intelligence, an Ottawa-based information security firm, told CTV Newsnet that he believes the worm is "far from a hoax."

"It's one of the biggest bot-nets we've ever seen," he said.

Davis recommended that Canadian computer users make sure their Microsoft Windows update is working and that their anti-virus software is up to date.

He said that on April 1, when the worm goes live, the average user wouldn't notice it operating on their computer as it will run hidden.

CIRA says it is registering and isolating unregistered dot-ca domain names that are expected to be generated by the Conficker worm.

Abel says that there are tools online that will search and destroy the worm if you think your computer is infected.