W32.Blaster.T.Worm - Removal

---

Important Notes:

• W32.Blaster.T.Worm exploits the DCOM RPC vulnerability. This is described in Microsoft Security Bulletin MS03-026, and a patch is available there. You must download and install the patch. In many cases, you will need to do this before continuing with the removal instructions. If you are not able to remove the infection or prevent re-infection using the following instructions, first download and install the patch.
• Because of the way the worm works, it may be difficult to connect to the Internet to obtain the patch, definitions, or a removal tool before the worm shuts down the computer. There are at least two known ways to work around this, although both solutions do not work 100% completely all the time.
  
  • If you run Windows XP, activating the Windows XP firewall may allow you to download and install the patch, obtain virus definitions, and run the removal tool. This may also work with other firewalls, although this has not been confirmed.
    
  • In many cases, on both Windows 2000 and XP, changing the settings of the Remote Call Procedure (RPC) service may allow you to connect to the Internet without shutting down the computer.
    
    Follow these steps:
    1. Do one of the following:
       • Windows 2000: Right-click the My Computer icon on the Windows desktop, and then click Manage. The Computer Management window opens.
       • Windows XP: Click the Start button, right-click the My Computer icon, click Manage. The Computer Management window opens.
         
         
    2. In the left pane, double-click Services and Applications, and then select Services. A list of services appears.
    3. In the right pane, locate the Remote Procedure Call (RPC) service.
       
       CAUTION: There is also a service named Remote Procedure Call (RPC) Locator. Do not confuse the two.
       
       
    4. Right-click the Remote Procedure Call (RPC) service, and then click Properties.
    5. Click the Recovery tab.
    6. Using the drop-down lists, change First failure, Second failure, and Subsequent failures to "Restart the Service."
    7. Click Apply, and then click OK.
       
       CAUTION: Make sure that you change these settings back when you have removed the worm.

---

The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

1. Disable System Restore (Windows XP).
2. Update the virus definitions.
3. Restart the computer in Safe mode or VGA mode.
4. Run a full system scan and delete all the files detected as W32.Blaster.T.Worm.
5. Reverse the changes that the Trojan made to the registry.
   

For specific details on each of these steps, read the following instructions.

1. To disable System Restore (Windows XP)
If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.

Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.

For instructions on how to turn off System Restore, read your Windows documentation, or one of the following articles:

• "How to disable or enable Windows Me System Restore"
• "How to turn off or turn on Windows XP System Restore"

For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article, "Antivirus Tools Cannot Clean Infected Files in the _Restore Folder," Article ID: Q263455.

2. To update the 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:

• Running LiveUpdate, which is the easiest way to obtain virus definitions: These virus definitions are posted to the LiveUpdate servers once each week (usually on Wednesdays), unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, refer to the Virus Definitions (LiveUpdate).
• 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.

3. To restart the computer in Safe mode or VGA mode
Shut down the computer and turn off the power. Wait for at least 30 seconds, and then restart the computer in Safe mode or VGA mode.

• For Windows 95, 98, Me, 2000, or XP users, restart the computer in Safe mode. For instructions, read the document, "How to start the computer in Safe Mode."
• For Windows NT 4 users, restart the computer in VGA mode.
  

4. To scan for and delete the infected files

1. 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."
2. Run a full system scan.
3. If any files are detected as infected with W32.Blaster.T.Worm, click Delete.

5. To reverse the changes made to the registry

---

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.

---

1. Click Start, and then click Run. (The Run dialog box appears.)
2. Type regedit
   
   Then click OK. (The Registry Editor opens.)
   
   
3. Navigate to the key:
   
   HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
   
   
4. In the right pane, delete the value:
   
   • "Helper" = "%System%\eschlp.exe /fstart"
   • "MSUpdate" = "%System%\svchosthlp.exe"
     
     
5. Delete the key:
   
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Sysuser
   
   
6. Exit the Registry Editor.

Technical Details