Backdoor.GWGirl

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Discovered: April 05, 2002
Updated: February 13, 2007 12:00:23 PM
Type: Trojan Horse


Backdoor.GWGirl is a Trojan that allows unauthorized access to an infected computer.

Antivirus Protection Dates

  • Initial Rapid Release version April 08, 2002
  • Latest Rapid Release version May 07, 2019 revision 006
  • Initial Daily Certified version April 08, 2002
  • Latest Daily Certified version May 07, 2019 revision 008
  • Initial Weekly Certified release date April 10, 2002

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.


Technical Description


Backdoor.GWGirl uses port 6267. It configures itself to run as a service.

When the Trojan is executed, it drops the following files:

  • \Windows\System\Diagcfg.exe
  • \Windows\System\Msiesmtp.dll.

It also makes the following changes to the Windows registry:
  • HKEY_CLASSES_ROOT\comfile\shell\open\command
    It adds diagcfg.exe in front of ""%1"%*".
  • HKEY_CLASSES_ROOT\exefile\shell\open\command
    It adds diagcfg.exe in front of ""%1"%*".
  • HKEY_LOCAL_MACHINE\Software\classes\comfile\shell\open\command
    It adds diagcfg.exe in front of ""%1"%*".
  • HKEY_LOCAL_MACHINE\Software\classes\exefile\shell\open\command
    It adds diagcfg.exe in front of ""%1"%*".
  • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\runServices
    It sets diagcfg.exe as the Default key value and adds a key named DiagnosticConfiguration with diagcfg.exe as the value.


Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
  • Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
  • Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.


Removal


Remove the changes that the Trojan made to the registry, restart the computer in Safe mode, and then delete the files \Windows\System\Diagcfg.exe and \Windows\System\Msiesmtp.dll. Detailed instructions follow.

NOTE: If the Trojan has executed, you must do the following:

  • You must modify the registry before removing Diagcfg.exe because .exe and .com files will look for this file in order to run.
  • You must make of copy of Regedit.exe as Regedit.com before you can run the Registry Editor.

Remove the changes that the Trojan made to the registry
Copy Regedit.exe to Regedit.com
Because the Trojan modified the registry so that you cannot run .exe files, you must first make a copy of the Registry Editor as a file with the .com extension and then run that.
  1. Do one of the following, depending on which version of Windows you are running:
    • Windows 95/98 users: Click Start, point to Programs, and click MS-DOS Prompt.
    • Windows Me users: Click Start, point to Programs, point to Accessories, and then click MS-DOS Prompt.
    • Windows NT/2000/XP users:
      1. Click Start, and click Run.
      2. Type the following and then press Enter:

        command

        A DOS window opens.
      3. Type the following and then press Enter:

        cd \winnt
      4. Go on to the next step.
  2. Type the following, and then press Enter:

    copy regedit.exe regedit.com
  3. Type the following, and then press Enter:

    start regedit.com

    NOTE: The Registry Editor opens in front of the DOS window. After you finish editing the registry and close Registry Editor, close the DOS window.
  4. Proceed to the following section Edit the registry, and remove keys and changes that the Trojan made only after you have accomplished the previous steps.

    Edit the registry, and remove keys and changes that the Trojan made

    CAUTION : We strongly recommend that you back up the registry before you make any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify only the keys that are specified. Read the document How to make a backup of the Windows registry for instructions.
    1. Click Start, and click Run. The Run dialog box appears.
    2. Type regedit and then click OK. The Registry Editor opens.
    3. Navigate to and select the following key:

      HKEY_CLASSES_ROOT\exefile\shell\open\command

      CAUTION: The HKEY_CLASSES_ROOT 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 an .exe extension from running. Make sure you browse all the way along this path until you reach the \command subkey.
      Do not
      modify the HKEY_CLASSES_ROOT\.exe key.
      Do modify the HKEY_CLASSES_ROOT\exefile\shell\open\command subkey that is shown in the following figure:


      <<=== NOTE: This is the key that you need to modify.

    4. Double-click the (Default) value in the right pane.
    5. Delete the current value data, and then type: "%1" %* (That is, type the following characters: quote-percent-one-quote-space-percent-asterisk.)

      NOTE: On computers that run Windows 9x and Windows NT, the Registry Editor will automatically enclose the value within quotation marks. When you click OK, the (Default) value should look exactly like this: ""%1" %*" On Windows 2000/XP-based systems, the additional quotation marks will not appear. On Windows 2000/XP-based systems, the (Default) value should look exactly like this: "%1" %*
    6. Make sure you that completely delete all value data in the command key prior to typing the correct data. If you accidentally leave a space at the beginning of the entry, any attempt to run program files will result in the error message, "Windows cannot find .exe." or "Cannot locate C:\ <path and file name>."
    7. Repeat this procedure to for these keys:

      HKEY_CLASSES_ROOT\comfile\shell\open\command
      HKEY_LOCAL_MACHINE\Software\classes\comfile\shell\open\command
      KEY_LOCAL_MACHINE\Software\classes\exefile\shell\open\command
    8. Navigate to the key

      HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServices
    9. In the right pane, double-click (Default) and delete the contents so that the line is empty.
    10. In the left pane, delete the DiagnosticConfiguration subkey.

    Restart the computer in Safe mode
    All Windows 32-bit operating systems except Windows NT can be restarted in Safe mode. Read the document for your operating system.
    Remove the Trojan
    Use Windows Explorer to delete the files \Windows\System\Diagcfg.exe and \Windows\System\Msiesmtp.dll. Restart the computer, and run a full system scan.


    Writeup By: Maryl Magee