Norton Antivirus 2003, Symantec's well-known desktop software, will scan files transferred over instant messengers for malicious viruses, Trojans and worms. Antivirus software has guarded email messages from harm, but IM users have been virtually left out in the cold.

The antivirus software, which is geared toward the consumer and small business, is designed to work on instant messengers from Yahoo, MSN and AOL. Symantec is aiming at pushing its IM cleansing technology into the enterprise arena within a year, according to Laura Garcia-Manrique, a senior product manager at Symantec, but they moved on the consumer market first because of IM's enormous popularity there.

''The more people use instant messaging, the more attackers will use instant messaging,'' says Garcia-Manrique. ''The more people use IM to share information and files, it's a natural evolution for viruses to begin using those vehicles.''

Symantec's announcement comes on the heals of a warning that IM users are being duped into downloading viruses and opening the door to intruders who use their systems to launch distributed attacks across the Net. Hackers are increasingly attacking systems through instant messaging, said Art Manion, Internet Security Analyst at CERT, a federally funded high-tech research and development center at Carnegie Mellon University.

In a recent interview, Manion says CERT has tens of thousands of reports of systems being compromised through instant messengers. ''Instant messaging is being used a lot and people aren't paying attention to the security risks that are out there,'' said Manion. ''People are still way too trusting, and they think instant messaging can't be used against them. But it can.''

Garcia-Manrique also notes that Symantec is handling some of the decision making for users.

She explains that currently when the antivirus software detects malicious code, an alert dialogue box will pop up asking the user if she wants to delete the virus, quarantine it or repair it. The new version, which will be widely available next month, will delete the virus automatically and then alert the user that it was taken care of.

''We did that because we've seen for the most part that the average home user doesnt know how to react if a virus is found on the system,'' says Garcia-Manrique, who adds that any user who wants manual control can change the default setting. ''It's safer for the antivirus software to delete a virus or repair something that is broken.