Backdoor.Nibu.F

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Discovered: May 17, 2004
Updated: February 13, 2007 12:20:59 PM
Type: Trojan Horse
Systems Affected: Windows


Backdoor.Nibu.F is a Trojan horse that attempts to steal passwords and bank account information.

Note: Virus definitions dated May 17, 2004 may detect this threat as W32.Dumaru.AJ@mm.

Antivirus Protection Dates

  • Initial Rapid Release version May 17, 2004
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version May 17, 2004
  • Latest Daily Certified version September 28, 2010 revision 036
  • Initial Weekly Certified release date May 19, 2004

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

Writeup By: Yuhui Huang

Discovered: May 17, 2004
Updated: February 13, 2007 12:20:59 PM
Type: Trojan Horse
Systems Affected: Windows


When Backdoor.Nibu.F is executed, it does the following:

  1. Copies itself as these files:
    • %System%\Load32.exe
    • %System%\Vxdmgr32.exe
    • %Startup%\Rundllw.exe


      Notes:
      • %System% is a variable. The worm locates the System folder and copies itself to that location. By default, this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).
      • %Startup% is a variable. The worm locates the Windows startup folder and copies itself to that location. For example, this is C:\Windows\Start Menu\Programs\Startup (Windows 95/98/Me) or C:\Documents and Settings\<current user>\Start Menu\Programs\Startup (Windows NT/2000/XP).
      • %Windir% is a variable. The worm locates the Windows installation folder (by default, this is C:\Windows or C:\Winnt) and copies itself to that location.


  2. Adds the following value:

    "load32"="%System%\load32.exe"

    to the following registry key:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

    so that the Trojan runs when you start Windows.

  3. Modifies the value data of:

    Shell

    in the following registry key:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Winlogon

    from:

    "explorer.exe"

    to:

    "explorer.exe %Windir%\system32\vxdmgr32.exe"

    so that the worm runs when you start Windows NT/2000/XP.

  4. Modifies the [boot] section of the System.ini file (Windows 95/98/Me only) to:

    [boot]
    shell=explorer.exe %System%\vxdmgr32.exe

    so that the worm runs when you start Windows 95/98/Me.

  5. Looks for windows that have certain strings in the title bar. These strings vary, but may include the following:
    • Bank
    • bank
    • bull
    • Bull
    • cash
    • ebay
    • e-metal
    • Fethard
    • fethard
    • gold
    • Keeper
    • localhost
    • mull
    • PayPal
    • Storm
    • WebMoney
    • Winamp
    • WM Keeper


      Note: Typically, such windows would be Web browser windows that display logon screens for financial services or email accounts.

  6. Captures keystrokes that are typed into windows that contain the previously listed strings and stores them in a log file. This file may be named %Windir%\vxdload.log.

  7. Launches a thread that monitors the Clipboard, saving to a log file any data that it finds. The file may be named %Windir%\rundllx.sys.

  8. If the logon window for e-gold.com's SRK is visited, the Trojan will attempt to create screen shots of specific parts of that page.

  9. The Trojan can also steal passwords from the WebMoney and Far FTP accounts that are stored in the registry.

  10. Periodically checks the size of the files it uses for logging stolen information. When the files are a certain size, the log files will be emailed to a hard-coded email address, along with System information such as the IP address and operating system. The Trojan also attaches the previously mentioned screen shots.


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.

Writeup By: Yuhui Huang

Discovered: May 17, 2004
Updated: February 13, 2007 12:20:59 PM
Type: Trojan Horse
Systems Affected: Windows


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.F.
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:
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.



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 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


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.
  1. Do one of the following:
    • Windows 2000/XP: Skip to step b.
    • Windows 95/98/Me: Click Start, and then click 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%\load32.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 %Windir%\system32\vxdmgr32.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, and then click OK.

    edit c:\windows\system.ini

    (The MS-DOS Editor opens.)

    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%\vxdmgr32.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, and then press S.
  6. Press Alt, and then press 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.
  2. Run a full system scan.
  3. If any files are detected as infected with Backdoor.Nibu.F, click Delete.
  4. Restart the computer in Normal mode.



Writeup By: Yuhui Huang