Trojan.Webus.C - Removal

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

Important: On computers running Norton AntiVirus 2005 or later, the QuickScan tool will automatically search for and remove malicious threats when new virus definitions are downloaded. While every effort has been made to ensure that the QuickScan tool removes all the traces of a malicious threat from an infected computer, we advise that you confirm that all the files and registry entries have been removed. We recommend following the manual removal steps and deleting any threat-related files or registry entries remaining on the computer.

1. Disable System Restore (Windows Me/XP).
2. Update the virus definitions.
3. Restart the computer in Safe mode or end the malicious process.
4. Run a full system scan and delete all the files detected as Trojan.Webus.C.
5. Delete the value that was added to the registry.
   

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

1. To disable System Restore (Windows Me/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"

Note: After you have completed the removal procedure and are satisfied that the threat has been removed, re-enable System Restore by following the instructions in the previously mentioned documents.

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:

• Run 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).
• Download the definitions using the Intelligent Updater
  The Intelligent Updater virus definitions are posted daily. 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 end the malicious process

To restart the computer in Safe mode in Windows 95/98/Me
Shut down the computer and turn off the power. Wait for at least 30 seconds, and then restart the computer in Safe mode. For instructions, read "How to start the computer in Safe Mode."

To end the malicious process in Windows NT/2000/XP

1. Press Ctrl+Alt+Delete once.
2. Click Task Manager.
3. On the Processes tab, double-click the Image Name column header to alphabetically sort the processes.
4. Scroll through the list, and look for Lassa.exe.
5. If you find the file, click it, and then click End Process.
6. Exit the Task Manager.

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 "How to configure Norton AntiVirus to scan all files."
   • For Symantec AntiVirus Enterprise products, read "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 Trojan.Webus.C, click Delete.
   
   
   Note: If your Symantec antivirus product reports that it cannot delete an infected file, Windows may be using the file. To fix this, run the scan in Safe mode. For instructions, read "How to start the computer in Safe Mode." After you have restarted the computer in Safe mode, run the scan again.
   
   After you delete the files, you may leave the computer in Safe mode and proceed with section 5. After you have finished step 5, restart the computer in Normal mode.
   

5. To delete the value from the registry

Important: 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. On the Windows taskbar, click Start > Run.
2. Type the following:
   
   regedit
   
   
3. Click OK.
   
   
4. Navigate to the following key:
   
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
   
   
5. In the right pane, delete the following value:
   
   ".mscdr" = "%System%\lassa.exe"
   
   
6. Exit the Registry Editor.

Technical Details