W32.HLLW.Nettrash - Removal

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 Me/XP).
2. Update the virus definitions.
3. Run a full system scan and delete all the files detected as W32.HLLW.Nettrash.
4. Delete the values that were added to the registry.
5. Edit the Win.ini file (Windows 95/98/Me).
   

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

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Notes:

• If the Trojan has not yet run—that is, the Trojan's file was copied to your computer but has not run—you should be able to follow the instructions in sections 1 through 3, which discuss detecting and removing this file.
• If the Trojan has run, in some cases you will not be able to follow these instructions, as the modifications that the Trojan made will prevent you from doing so. In this situation, first follow the instructions in section 4 to edit the registry. After you complete those instructions, follow the steps in sections 1 through 3..

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WARNING: If you are running Windows 95/98/Me, do not restart your computer until you have removed the Trojan.

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1. Disabling 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"
  

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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.

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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. Updating 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. Scanning for and deleting 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.HLLW.Nettrash, click Delete.

4. Deleting the value from the registry

Copying Regedit.exe to Regedit.com and editing the registry
Because the Trojan modified the registry so that the Trojan runs when you run the .exe files, first make a copy of the Registry Editor as a file with the .com extension, and then run the file.

1. Do one of the following, depending on the version of Windows you are running:
   • Windows 95/98 users:
     1. Click Start.
     2. Point to Programs.
     3. Click the MS-DOS Prompt. (A DOS window opens at the C:\Windows prompt.) Proceed to step B of this section.
        
        
   • Windows Me users:
     1. Click Start.
     2. Point to Programs.
     3. Point to Accessories.
     4. Click the MS-DOS Prompt. (A DOS window opens at the C:\Windows prompt.) Proceed to step B of this section.
        
        
   • Windows NT/2000 users:
     1. Click Start, and then click Run.
     2. Type command, and then press Enter. (A DOS window opens.)
     3. Type cd \winnt, and then press Enter.
     4. Go to step B of this section.
        
        
   • Windows XP users:
     1. Click Start, and then click Run.
     2. Type command, and then press Enter. (A DOS window opens.)
     3. Type the following:
        
        cd\
        cd \windows
        
        Press Enter after typing each one.
        
     4. Proceed to step B of this section.
        
        
2. Type copy regedit.exe regedit.com
   
   and then press Enter.
   
   
3. Type start regedit.com
   
   and then press Enter. (The Registry Editor opens in front of the DOS window.)
   
   After you finish editing the registry, exit the Registry Editor, and then exit the DOS window as well.
   
   
4. Before continuing, 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. For instructions, read the document, "How to make a backup of the Windows registry."
   
   
5. Navigate to and select the key:
   
   HKEY_LOCAL_MACHINE\Software\Classes\exefile\shell\open\command
   
   NOTE: The HKEY_LOCAL_MACHINE\Software\Classes key contains many subkey entries that refer to other file extensions. One of these file extensions is .exe. Changing this extension can prevent any files ending with a .exe extension from running. Make sure that you completely browse through this path until you reach the \command subkey.
   
   Modify the HKEY_LOCAL_MACHINE\Software\Classes\exefile\shell\open\command subkey, shown in the following figure:
   
   <<=== NOTE: Modify this key.
   
   
6. In the right pane, double-click the (Default) value.
7. Delete the current value data, and then type:
   
   "%1" %*
   
   That is, type the characters: quote-percent-one-quote-space-percent-asterisk.
   
   NOTES
   • Under Windows 95/98/Me/NT, the Registry Editor automatically encloses the value within quotation marks. When you click OK, the (Default) value should look exactly like this:
     
     ""%1" %*"  
     
   • Under Windows 2000/XP, the additional quotation marks will not appear. When you click OK, the (Default) value should look exactly like this:
     
     "%1" %*
     
   • Make sure that you completely delete all the value data in the command key before typing the correct data. If you leave a space at the beginning of the entry, any attempt to run the program files will result in the error message, "Windows cannot find .exe." If this occurs, restart the entire process from the beginning of this document and make sure that you completely remove the current value data.
     
     
8. Navigate to the key:
   
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
   
   
9. In the right pane, delete the value:
   
   "User32"="<path to original file name>"
   
   
10. In the right pane, delete the value:
    
    "<original app name>" = "<path to original file name>"
    
    
11. Exit the Registry Editor.

5. Editing the Win.ini file
If you are running Windows 95/98/Me, follow these steps:

1. The function you perform depends on your operating system:
   • Windows 95/98: Go to step B.
   • Windows Me: If you are running Windows Me, the Windows Me file-protection process may have made a backup copy of the Win.ini file that you need to edit. If this backup copy exists, it will be in the C:\Windows\Recent folder. Symantec recommends that you delete this file before continuing with the steps in this section. To do this:
     1. Start Windows Explorer.
     2. Browse to and select the C:\Windows\Recent folder.
     3. In the right pane, select the Win.ini file and delete it. The Win.ini file will be regenerated when you save your changes to it in step F.
        
        
2. Click Start, and then click Run.
3. Type the following, and then click OK.
   
   edit c:\windows\win.ini
   
   (The MS-DOS Editor opens.)
   
   
4. In the [windows] section of the file, look for a line similar to:
   
   run=<original file name of Trojan>
   
   
5. If this line exists, delete everything to the right of run=.
   
   
6. Click File, and then click Save.
7. Click File, and then click Exit.

Technical Details