Remember that Wi-Fi hack demo at the Blackhat conference a couple of months ago?
Quietly tonight, Microsoft released a really major update to help prevent that hack method. What's unusual about this release is that it includes new features, something normally reserved for add-on modules or service packs.
It's really part of a feature update to bring Windows XP into parity with domain policy features for the upcoming Windows Server 2003 Service Pack 2 . . . but it's much more than that, and in my opinion, an important update to install. I rather hope that Microsoft places this on their update site, but for now, you have to go the the KB article on the topic to get the patch.