Worms that are traditionally targeting MSN will also target the Yahoo users,
Last year, instant messaging was the sleeping giant, and companies were literally asleep at the wheel. This year, people are awakening to the problem, but haven't necessarily come up with solutions.
These are real-time communication networks that are on disparate technology standards. There are some significant challenges.
The difficulty is that worm developers are using tactics that have been successful in e-mail campaigns. They're able to mutate earlier worms and try different strategies, and that's giving them a level of sophistication.