Microsoft a few hours ago released an unscheduled update for pretty much all versions of Windows. They normally release updates once a month, but today they released an out-of-band updated because of the severity of the attack vector. It’s pretty bad in that it allows someone to gain access to your computer if you have file-sharing enabled. You can read more about it here and here, but the important thing to do is to be sure that you always run Windows Update whenever you get the opportunity to install new patches and fixes. Here’s how to do it.
For Windows Vista users
From your start menu, run “Windows Update” and install all critical, recommended and optional updates.