It's all over the place where I work... traffic from it and Welchia brought down our network for about an hour yesterday.. someone had brought Welchia in on a laptop, so our local subnet was getting hammered, and sobig was nailing the exchange server from the outside just as hard.

Headaches abound.

What sucks is, it's hard to filter it without filtering important stuff in a business environment. You just have to keep running NAV and eyeballing the incoming/outgoing queues.