Backdoor.Zagaban - 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 or Safe mode with Command Prompt.
4. Run a full system scan and delete all the files detected.
5. Restore any modified values 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: When you are completely finished with the removal procedure and are satisfied that the threat has been removed, reenable 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 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 Virus Definitions (Intelligent Updater).
  
  The latest Intelligent Updater virus definitions can be obtained here: Intelligent Updater virus definitions. For detailed instructions read the document: How to update virus definition files using the Intelligent Updater.

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 the next section.

Windows 2000

1. Shut down the computer, and then 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 (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 the next section.

Windows XP

1. Shut down the computer, and then 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 will 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 the next section.
   

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 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, click Delete.

5. To restore the modified value in 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. For instructions refer to the document: How to make a backup of the Windows registry.

1. Click Start > Run.
2. Type regedit
3. Click OK.
   
   Note: If the registry editor fails to open the threat may have modified the registry to prevent access to the registry editor. Security Response has developed a tool to resolve this problem. Download and run this tool, and then continue with the removal.
   
   
4. Navigate to the subkey:
   
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
   
   
5. In the right pane, restore the value from:
   
   "Shell" = "explorer.exe %System%\gld.exe"
   
   to the default value, which is usually:
   
   "Shell" = "explorer.exe"
   
   
6. Exit the Registry Editor.
   
   
7. Restart the computer in Normal Mode.

Technical Details