Microsoft typically releases updates for Windows on the 2nd Tuesday of each month (aka Patch Tuesday), but this week, they released an important patch outside of their normal schedule.

The security bulletin describes the details. An issue with the “server service,” part of the Windows operating system, could allow your Windows computer to be taken over in a “worm attack” similar to the SQL Slammer attack that occurred in January, 2003.

This issue is considered “critical” for Windows 2000, XP and Server 2003 and “important” for Windows Vista and Server 2008. Check if your system is up-to-date at the Windows Update site.