Backdoor.Nibu.E - 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. Restart the computer in Safe mode (Windows 95/98/Me) or Safe mode with Command Prompt (Windows 2000/XP).
4. Reverse the changes made to the registry.
5. Reverse the changes made to the System.ini (Windows 95/98/Me).
6. Restart the computer in Safe mode or VGA mode (Windows 2000/XP).
7. Run a full system scan and delete all the files detected as Backdoor.Nibu.E.
8. Delete the DNS entries added to the Windows hosts file.
   

For 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 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.

Note: If you receive error messages when you run LiveUpdate, first follow the instructions in section 8. Then return to section 2 and continue with the removal.

3. To restart the computer in Safe mode or Safe mode with Command Prompt
Follow the instructions for your operating system.

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 the document, "How to start the computer in Safe Mode."

Once in Safe mode (this could take some time), proceed with section 4.

Windows 2000

1. Shut down the computer and turn off the power. Wait for at least 30 seconds, and then restart the computer
2. When you see the black and white Starting Windows bar at the bottom of the screen, press the F8 key. (This is usually on the top row of the keyboard.)
3. In the Windows 2000 Advanced Options Menu, select Safe mode with Command Prompt, and then press Enter.
   
   Once the computer opens to a window with a command prompt (you should see a line of text and a blinking cursor), proceed with section 4.

Windows XP

1. Shut down the computer and turn off the power. Wait for at least 30 seconds, and then restart the computer. The computer begins processing a set of instructions known as the Basic Input/Output System (BIOS). What is displayed depends on the BIOS manufacturer. Some computers display a progress bar that refers to the word BIOS, while others may not display any indication that this process is occurring.
2. As soon as the BIOS has finished loading, begin tapping the F8 key on your keyboard. Continue to do so until the Windows Advanced Options menu appears. If you begin tapping the F8 key too soon, some computers display a "keyboard error" message. To avoid this, restart the computer and try again.
3. In the Windows 2000 Advanced Options Menu, select Safe mode with Command Prompt, and then press Enter.
   
   Once the computer opens to a window with a command prompt (you should see a line of text and a blinking cursor), proceed with section 4.

4. To reverse the changes made to 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. Do one of the following:
   • Windows 2000/XP. Skip to step b.
   • Windows 95/98/Me. Click Start > Run.
     
     
2. Type the following:
   
   regedit
   
   
3. Do one of the following:
   • Windows 2000/XP: Press Enter.
   • Windows 95/98/Me: Click OK.
     
     
4. Navigate to the key:
   
   HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
   
   
5. In the right pane, delete the value:
   
   "load32"="%System%\netda.exe..."
   
   
6. Do one of the following:
   • Windows 95/98/Me. Skip to step i..
   • Windows NT/2000/XP: Proceed with step g.
     
     
7. Navigate to the key:
   
   HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Winlogon
   
   
8. In the right pane, double-click:
   
   Shell
   
   
9. Change:
   
   explorer.exe %System%\netdc.exe
   
   to:
   
   explorer.exe
   
   
10. Exit the Registry Editor.
    
    
11. Do one of the following:
    • Windows 95/98/Me. Proceed with section 5.
    • Windows NT/2000/XP: Skip to section 6.

5. To reverse the changes made to the System.ini file (Windows 95/98/Me only)
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 System.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 System.ini file will be regenerated when you save your changes to it in step F.
        
        
2. Type the following.
   
   edit c:\windows\system.ini
   
   and then click OK.
   
   Note: If Windows is installed in a different location, make the appropriate path substitution.
   
   
3. In the [boot] section of the file, look for a line similar to:
   
   Shell="explorer.exe %System%\netdc.exe"
   
   
4. If this line exists, delete everything to the right of Explorer.exe.
   
   When you are done, it should look like:
   
   shell=Explorer.exe
   
   
5. Press Alt > S.
   
   
6. Press Alt > X.
   
   
7. Skip to section 7.

6. 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. For instructions, read the document, "How to start the computer in Safe Mode."


7. 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 file."
2. Run a full system scan.
3. If any files are detected as infected with Backdoor.Nibu.E, click Delete.

8. To delete the DNS entries added to the Windows hosts file

Note: The location of the Hosts file may vary and some computers may not have this file. For example, if the file exists in Windows 98, it will usually be in C:\Windows; and it is located in the C:\WINNT\system32\drivers\etc folder in Windows 2000. There may also be multiple copies of this file in different locations.

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.

Technical Details