Contributed By: Cliff Hobbs [MVP SMS]
Here is some information on how to patch and cleanup any machines that either infected or vulnerable to this Worm.

Instructions for Patching and Cleaning Vulnerable Windows 2000 and Windows XP systems:
Vulnerable Windows 2000 and Windows XP machines may have the LSASS.EXE process crash every time a malicious worm packet targets the vulnerable machine which can occur very shortly after the machine starts up and initializes the network stack.

When cleaning a machine that is vulnerable to the Sasser worm it is necessary to first prevent the LSASS.EXE process from crashing, which in turn causes the machine to reboot after a 60 second delay.  This reboot cannot be aborted on Windows 2000 platforms using the Shutdown.exe or psshutdown.exe utilities and can interfere with the downloading and installation of the patch as well as removal of the worm.

1. To prevent LSASS.EXE from shutting down the machine during the cleaning process:

     a. Unplug the network cable from the machine

     b. If you are running Windows XP you can enable the built-in Internet Connection Firewall using the instructions found here: Windows XP

http://support.microsoft.com/?id=283673 and then plug the machine back into the network and go to step 2.

     c. If you are running Windows 2000, you won't have a built-in firewall and must use the following work-around to prevent LSASS.EXE from crashing.

This workaround involves creating a read-only file named 'dcpromo.log' in the "%systemroot%\debug" directory.  Creating this read-only file will prevent the vulnerability used by this worm from crashing the LSASS.EXE process.

         i.      NOTE:  %systemroot% is the variable that contains the name of the Windows installation directory.  For example if Windows was installed to the "c:\winnt" directory the following command will create a file called dcpromo.log in the c:\winnt\debug directory.  The following commands must be typed in a command prompt (i.e. cmd.exe) exactly as they are written below.

      1. To start a command shell, click Start and then click run and type 'cmd.exe' and press enter.

      2.Type the following command:

       echo dcpromo >%systemroot%\debug\dcpromo.log

      For this workaround to work properly you MUST make the file read-only by typing the following command:

      3. attrib +R %systemroot%\debug\dcpromo.log

2. After enabling the Internet Connection Firewall or creating the read-only dcpromo.log you can plug the network cable back in and you must download and install the MS04-011 patch from the MS04-011 download link for the affected machines operating system before cleaning the system.  If the system is cleaned before the patch is installed it is possible that the system could get re-infected prior to installing the patch.

     a. Here is the URL for the bulletin which contains the links to the download location for each patch:

http://www.microsoft.com/technet/security/bulletin/ms04-011.mspx

     b. If your machine is acting sluggish or your Internet connection is slow you should use Task Manager to kill the following processes and then try downloading the patch again (press the Ctrl + Alt + Del keys simultaneously and select Task Manager):

  i. Kill any process ending with '_up.exe' (i.e. 12345_up.exe)

  ii. Kill any process starting with 'avserv' (i.e. avserve.exe, avserve2.exe)

  iii. Kill any process starting with 'skynetave' (i.e. skynetave.exe)

  iv. Kill hkey.exe

  v. Kill msiwin84.exe

  vi. Kill wmiprvsw.exe

Note: there is a legitimate system process called 'wmiprvse.exe' that does NOT need to be killed.

          c. Allow the system to reboot after the patch is installed.

3. Run the Sasser cleaner tool from the following URL:

     a. For the on-line ActiveX control based version of the cleaner you can run it directly from the following URL:

http://www.microsoft.com/security/incident/sasser.asp

     b. For the stand-alone download version of the cleaner you can download it from the following URL:

http://www.microsoft.com/downloads/details.aspx?FamilyId=76C6DE7E-1B6B-4FC3-90D4-9FA42D14CC17&displaylang=en

4. Determine if the machine has been infected with a variant of the Agobot worm which can also get on the machine using the same method as the Sasser worm.

     a. To do this run a full antivirus scan of your machine after ensuring your antivirus signatures are up to date.

     b. If you do NOT have an antivirus product installed you can visit HouseCall from TrendMicro to perform a free scan using the following URL:

http://housecall.trendmicro.com/

If you have any questions regarding the security updates or its implementation after reading the above listed bulletin you should contact Product Support Services in the United States at 1-866-PCSafety (1-866-727-2338).  International customers should contact their local subsidiary.