Microsoft has verified that a malicious worm known as W32.Sasser.worm and variants of that worm are spreading on the Internet. You can help protect your computer by downloading and installing Microsoft Security Update MS04-011.
If you have already installed the update, you are protected from the worm. If you have not already installed the update, you can download and install it from the Windows Update Web site. The update is listed in the critical updates under the update number 835732.