Trojan.Tooso.E - Removal

Removal using the W32.Beagle@mm Removal Tool
Symantec Security Response has developed a removal tool to clean the infections of Trojan.Tooso.E. Use this removal tool first, as it is the easiest way to remove this threat.

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

Before you begin: This threat may

1. Disable System Restore (Windows Me/XP).
2. Delete the value that was added to the registry and restart Windows.
3. Delete the lines that were added to the Windows Hosts file
4. Reinstall your Symantec antivirus program.
5. Update the virus definitions.
6. Run a full system scan and delete all the files detected as Trojan.Tooso.E.
   

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: When you are completely finished with the removal procedure and are satisfied that the threat has been removed, re-enable System Restore by following the instructions in the aforementioned 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 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 subkeys only. Read the document, "How to make a backup of the Windows registry," for instructions.

1. Click Start > Run.
   
   
2. Type regedit
   
   Then click OK.
   
   
3. Navigate to the subkeys:
   
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
   HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
   
   
4. In the right pane, delete the value:
   
   "winshost.exe" = "%Windir%\winshost.exe"
   
   
5. Exit the Registry Editor.
   
   
6. Restart Windows
   
   

3. To delete the lines that were added to the Windows Hosts file
Because this Trojan overwrites the Windows Hosts file, the contents of the file must be removed (except for one line) so that you can access many Web sites.

Note: If you are on a corporate network, you may have had a customized Hosts file. We suggest that you contact the network administrator before proceeding.

Follow the instructions for your operating system:

• Windows 95/98/Me/NT/2000
  1. Click Start, point to Find or Search, and then click Files or Folders.
  2. Make sure that "Look in" is set to (C:) and that "Include subfolders" is checked.
  3. In the "Named" or "Search for..." box, type:
     
     hosts
     
     
  4. Click Find Now or Search Now.
  5. For each Hosts file that you find, right-click the file, and then click Open With.
  6. Deselect the "Always use this program to open this program" check box.
  7. Scroll through the list of programs and double-click Notepad.
  8. When the file opens, delete all the entries in the Hosts file, except for the following line:
     
     127.0.0.1     localhost
     
  9. Close Notepad and save your changes when prompted.
     
     
• Windows XP
  1. Click Start > Search.
  2. Click All files and folders.
  3. In the "All or part of the file name" box, type:
     
     hosts
     
     
  4. Verify that "Look in" is set to "Local Hard Drives" or to (C:).
  5. Click More advanced options.
  6. Check Search system folders.
  7. Check Search subfolders.
  8. Click Search.
  9. Click Find Now or Search Now.
  10. For each Hosts file that you find, right-click the file, and then click Open With.
  11. Deselect the Always use this program to open this program check box.
  12. Scroll through the list of programs and double-click Notepad.
  13. When the file opens, delete all the entries in the Hosts file, except for the following line:
      
      127.0.0.1     localhost
      
  14. Close Notepad and save your changes when prompted.
      

4. To reinstall your Symantec antivirus program
As this virus attempts to remove the files and registry subkeys that your Symantec antivirus program uses, you may need to reinstall the program. If your Symantec antivirus program is not working properly, uninstall, and then reinstall it.


5. 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 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.
  
  

Note: If you see an error, such as LU1418, when you try to run LiveUpdate and you cannot get the Web site hosting the Intelligent Updater, it is likely that the worm has modified the Hosts file. You can either download and install LiveUpdate 2.5, which can remove Symantec entries from that file, or you can edit it yourself. See the instructions for both in the "Additional Information" section below.


6. 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 Trojan.Tooso.E, 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 the document, "How to start the computer in Safe Mode." Once you have restarted in Safe mode, run the scan again.

Technical Details