Microsoft has issued an alert over a vulnerability in Windows 2000 SP4, Windows 2003 SP1 and SP2 DNS. You can safely assume that if you are not running a supported version of these OS’s (previous to these service packs) then you are affected.
Jesper Johansson has posted a blog entry showing how to apply Microsoft’s recommended mitigation action to a large number of computers via a server listing and a command line configuration. It’s up to you if you wish to apply this change. My advice is to do it if you feel if you are seriously at risk. Make sure you have fully tested and have a back out plan that is also tested. In the end, it’s up to you what you do!
The Microsoft Security Response team has said that they are working around the clock to develop a working and stable fix that they can deploy to close the vulnerability off.