Removal using the W32.Blaster.Worm Removal Tool
Symantec Security Response has developed a removal tool to clean the infections of W32.Blaster.Worm. This is the easiest way to remove this threat and should be tried first.

Manual Removal
As an alternative to using the removal tool, you can manually remove this threat. The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.


Restore Internet connectivity.
End the worm process.
Obtain the latest virus definitions.
Scan for and delete the infected files.
Reverse the changes made to the registry.
Obtain the Microsoft HotFix to correct the DCOM RPC vulnerability.


For specific details, refer to the following instructions:

1. Restoring Internet connectivity
In many cases, on both Windows 2000 and XP, changing the settings for the Remote Procedure Call (RPC) service may allow you to connect to the Internet without the computer shutting down. To restore Internet connectivity to your PC, follow these steps:

Click Start > Run. The Run dialog box appears.
Type:

SERVICES.MSC /S

in the open line, and then click OK. The Services window opens.


In the right pane, locate the Remote Procedure Call (RPC) service.


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CAUTION: There is also a service named Remote Procedure Call (RPC) Locator. Do not confuse the two.
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Right-click the Remote Procedure Call (RPC) service, and then click Properties.
Click the Recovery tab.
Using the drop-down lists, change First failure, Second failure, and Subsequent failures to "Restart the Service."
Click Apply, and then OK.


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CAUTION: Make sure that you change these settings back once you have removed the worm.
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2. Ending the Worm process
Press Ctrl+Alt+Delete once.
Click Task Manager.
Click the Processes tab.
Double-click the Image Name column header to alphabetically sort the processes.
Scroll through the list and look for Msblast.exe.
If you find the file, click it, and then click End Process.
Exit the Task Manager.
3. Obtaining the latest virus definitions
Symantec Security Response fully tests all the virus definitions for quality assurance before they are posted to our servers. There are two ways to obtain the most recent virus definitions:

For newer computer users
Running LiveUpdate, which is the easiest way to obtain virus definitions: Virus definitions for W32.Blaster.worm have been made available via the LiveUpdate server since August 11th, 2003. To obtain the latest virus definitions, click the LiveUpdate button from within the main user interface of your Symantec product. When running LiveUpdate, ensure that only "Norton AntiVirus Virus Definitions" are checked. Product updates can be obtained at a later time.

For system administrators and advanced users
Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted on U.S. business days (Monday through Friday). You should download the definitions from the Symantec Security Response Web site and manually install them. To determine whether definitions for this threat are available by the Intelligent Updater, refer to the Virus Definitions (Intelligent Updater).

The Intelligent Updater virus definitions are available: Read "How to update virus definition files using the Intelligent Updater" for detailed instructions.

4. Scanning for and deleting the infected files
Start your Symantec antivirus program and make sure that it is configured to scan all the files.
For Norton AntiVirus consumer products: Read the document, "How to configure Norton AntiVirus to scan all files."
For Symantec AntiVirus Enterprise products: Read the document, "How to verify that a Symantec Corporate antivirus product is set to scan all files."
Run a full system scan.
If any files are detected as infected with W32.Blaster.Worm, click Delete.

5. Reversing the changes made to the registry

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CAUTION: Symantec strongly recommends that you back up the registry before making any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify the specified keys only. Read the document, "How to make a backup of the Windows registry," for instructions.
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Click Start, and then click Run. (The Run dialog box appears.)
Type regedit

Then click OK. (The Registry Editor opens.)


Navigate to the key:

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run


In the right pane, delete the value:

windows auto update


Exit the Registry Editor.

6. Obtaining the Microsoft HotFix to correct the DCOM RPC vulnerability
W32.Blaster.Worm is a worm that exploits the DCOM RPC vulnerability using TCP port 135 to infect your PC. The W32.Blaster.Worm also attempts to perform a DoS on the Microsoft Windows Update Web server (windowsupdate.com) using your PC. To fix this, it is important to obtain the Microsoft Hotfix at: Microsoft Security Bulletin MS03-026.



Additional information:

Additional information and an alternate site from which to download the Microsoft patch is available in the Microsoft article, "What You Should Know About the Blaster Worm and Its Variants."