Corey Bates was chatting on his MSN Messenger recently when his high school buddy Trey sent him a winking-face icon. Then Trey sent him another icon. Then another.

Bates, an 18-year-old who will start his freshman year at Oklahoma University this month, knew it was uncharacteristic of Trey to flood him with winking faces--a popular "emoticon" used to color text-based IM conversations. His suspicions grew when the alias "george.w.bush@whitehouse.gov" suddenly flashed on his screen along with an invitation to accept an attached file called "choke.exe." Unlike his friend, who obviously had been bitten by a virus, Bates knew better than to accept it.

"I was like, 'What the heck? Something is wrong,'" Bates said in an IM exchange with CNET News.com on Monday.

Having long targeted e-mail with sometimes devastating effects, virus and worm creators are setting their sights on IM services. Infected files, for example, have been burrowing their way slowly through Microsoft's MSN Messenger network over the past few months.

Discovered by virus hunters in late June, the so-called Choke worm marked the second attack aimed at MSN Messenger in as many months. In May, the service was struck by the W32/Hello worm. Security experts said they are as yet unaware of any virus attacks that might have targeted AOL Time Warner's AOL Instant Messenger (AIM) and ICQ or Yahoo's Yahoo Messenger.

Virus writers in search of the biggest bang for their bugs have targeted various types of networks, including peer-to-peer file exchanges and wireless Web systems. None have proven as effective as e-mail, however, where some viruses have rapidly gained the force of an avalanche through large corporate e-mail systems. Once a virus is activated, it can shoot itself out to everybody in a victim's address book, leading to an exponential growth rate.

IM viruses discovered so far have been relatively innocuous compared with virulent e-mail-borne infections such as the Love Bug, Anna Kournikova and Melissa.

"E-mail is still the most effective way to get viruses around," said Richard Smith, chief technology officer of the Privacy Foundation.

Nevertheless, some computer security experts say it is only a matter of time before similar outbreaks plague IM services.

Already, millions of people on the Internet communicate through instant messengers, which let people exchange text messages in real time and have become some of the most popular features on the Internet.

By Jim Hu
August 14, 2001 1:31 PM PT