W32.Gaobot.AZT - 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. Restart the computer in Safe mode or VGA mode.
3. Restore the Hosts file.
4. Reverse the changes made to the registry, and then restart the computer.
5. Update the virus definitions.
6. Run a full system scan and delete all the files detected as W32.Gaobot.AZT.
   

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

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Before you begin:
If you are running Windows NT/2000/XP, make sure that you do, or have done, the following:

• Create a secure password. This threat takes advantage of weak network passwords. (A full-time Internet connection, such as DSL or Cable, is considered a network connection for these purposes.)
• Patch the DCOM RPC vulnerability (described in Microsoft Security Bulletin MS03-026).
• Patch the RPC locator vulnerability (described in Microsoft Security Bulletin MS03-001).
• Patch the WebDav vulnerability (described in Microsoft Security Bulletin MS03-007).
• Patch the Workstation service buffer overrun vulnerability (described in Microsoft Security Bulletin MS03-049).

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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"

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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. 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.

3. To restore the Windows Hosts file

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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.

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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 one that you find, note its location. (This is displayed in the "In Folder" column.)
  6. Right-click each file, and then click "Open With."
  7. Deselect the "Always use this program to open this program" check box.
  8. Scroll through the list of programs and double-click Notepad.
  9. When the file opens, delete all the entries in the Hosts file, except for the following line:
     
     127.0.0.1     localhost
     
     
  10. Close Notepad and save your changes when prompted.
      
      
• Windows XP
  1. Click Start, and then click 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 one that you find, note its location. (This is displayed in the "In Folder" column.)
  11. Right-click each file, and then click "Open With."
  12. Deselect the "Always use this program to open this program" check box.
  13. Scroll through the list of programs and double-click Notepad.
  14. When the file opens, delete all the entries in the Hosts file except for the following line:
      
      127.0.0.1     localhost
      
      
  15. Close Notepad and save your changes when prompted.

4. To reverse the changes made to the registry

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WARNING: 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.

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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:
   
   "Windows Video Drivers" = "videons32.exe"
   
   
5. Do one of the following:
   • Windows NT/2000/XP. Skip to step h.
   • Windows 95/98/Me. Proceed with step f.
     
     
6. Navigate to the key:
   
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\
   RunServices
   
   
7. In the right pane, delete the value:
   
   "Windows Video Driver" = "videons32.exe"
   
   
8. Exit the Registry Editor.
   
   
9. Restart the computer in Normal mode. For instructions, read the section on returning to Normal mode in the document, "How to start the computer in Safe Mode."

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 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.

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 W32.Gaobot.AZT, click Delete.

Technical Details