Microsoft has issued a tool to plug the leak so to speak that would confound the worm. Technet.microsoft.com has a pretty good article about the whole thing, and what it does. They are also offering a $250,000 reward for infomration leading to the arrest of those responsible for making/deploying the virus. There are presently two known variants, Conficker A and B. They exploit the same leak in Windows, mostly in enterprise systems, so this was targeted mostly towards server lans, but it will infect anything that isn't already plugged off.

Most enterprise systems subscribe to the MSRT (Microsoft's malicious software removal tool service) and probably already have the security update that was issued last October. If you are concerned, here's the website that has the update:

http://www.microsoft.com/technet/security/Bulletin/MS08-067.mspx

While this worm may be rendered inert using antivirus and security update tools on individual machines, there could still be a lot of unprotected servers and workstations out there that will generate a lot of extraneous internet traffic if the worm activates, possibly slowing down the system a bit. I guess we will see what happens next wednesday.