Trojan.Bookmarker

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Discovered: December 20, 2003
Updated: February 13, 2007 12:15:36 PM
Type: Trojan Horse
Systems Affected: Windows


Trojan.Bookmarker is a small Trojan horse that modifies the Internet Explorer home page and search page, and adds bookmarks that point to pornographic Web sites to the Favorites folder.

This Trojan changes the Internet Explorer Home page to webcoolsearch.com. It is also packed with UPX.

Antivirus Protection Dates

  • Initial Rapid Release version December 22, 2003
  • Latest Rapid Release version January 15, 2018 revision 020
  • Initial Daily Certified version December 22, 2003 revision 004
  • Latest Daily Certified version January 15, 2018 revision 024
  • Initial Weekly Certified release date December 23, 2003

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

Writeup By: Yuhui Huang

Discovered: December 20, 2003
Updated: February 13, 2007 12:15:36 PM
Type: Trojan Horse
Systems Affected: Windows


Trojan.Bookmarker is distributed as an executable installer through Web browser exploits or downloaders.

When the installer program is executed, it does the following:

  1. Creates the file, %System%\Msconfd.dll. This file has the hidden attribute.


    Note: %System% is a variable. By default, this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).

  2. Invokes the Msconfd.dll file by executing this command:

    rundll32.exe msconfd,Restore

When the Msconfd.dll file is loaded, it does the following:
  1. Adds the value:

    "AppInit_DLLs"="msconfd.dll"

    to the registry key:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows

    so that the .dll file is loaded each time you start Windows NT/2000/XP.

  2. Adds the value:

    "Desktop" = "rundll32.exe %System%\msconfd.dll,Restore ControlPanel"

    to the registry key:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

    so that the dll is loaded every time you start Windows.

  3. Adds the value:

    "Desktop" = "<number>"

    to the registry key:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer


    Note:<number> is generated from the system time.

  4. Creates or overwrites the file, %System%\drivers\etc\hosts, with the text:

    127.0.0.1 localhost

  5. Adds the values:

    "Start Page"="http:/ /webcoolsearch.com"
    "Search Page"="http:/ /webcoolsearch.com"
    "Search Bar"="http:/ /webcoolsearch.com"

    to the registry key:

    HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main

  6. Adds the value:

    "SearchURL"="http:/ /webcoolsearch.com"

    to the registry key:

    HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer

  7. Adds the value:

    "SearchAssistant"="http:/ /webcoolsearch.com"

    to the registry key:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Internet Explorer\Search

  8. Creates several links to pornographic Web sites in the Favorites folder, and in the Links folder within the Favorites folder.

  9. If the Msconfd.dll is launched using the command:

    "rundll32.exe ...\msconfd,Restore..."

    the Trojan will return an error number, and Windows will display an error message indicating that the .dll initialization routine failed.


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: December 20, 2003
Updated: February 13, 2007 12:15:36 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. Run a full system scan and record the file names detected as Trojan.Bookmarker.
  4. Restart the computer in Safe mode.
  5. Search for the detected .dll file (Usually Msconfd.dll).
  6. Rename the file and extension.
  7. Restart the computer in Safe mode.
  8. Delete the value that was added to the registry.
  9. Run a full system scan and delete the files detected as Trojan.Bookmarker.
  10. Reset the Internet Explorer Home page.
  11. Reset the Internet Explorer Search page.
  12. Remove the links from the Favorites folder.
For specific details on each of these steps, read the following instructions.

1. Disabling 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. Updating 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. Scanning for and recording the names of the infected files
4. Restarting the computer in Safe 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 ."

5. Searching for the detected .dll file (Usually Msconfd.dll)
Follow the instructions for your operating system

Windows 95/98/Me/NT/2000
    1. On the Windows taskbar, click Start > Find or Search > Files or Folders.
    2. In the Search Results window, set "Look in" to (C:) and check "Include subfolders."
    3. In the "Named" or "Search for..." box, type the name of the .dll file that was detected as Trojan.Bookmarker.

      For example:

      msconfd.dll

    4. Click Find Now or Search Now.

Windows XP
    1. On the Windows taskbar, click Start > Search.
    2. Click All files and folders.
    3. In the "All or part of the file name" box, type the name of the .dll file that was detected as Trojan.Bookmarker.

      For example:

      msconfd.dll

    4. Verify that "Look in" is set to "Local Hard Drives" or to (C:).
    5. Click "More advanced options."
    6. Select "Search system folders."
    7. Select "Search subfolders."
    8. Select "Search hidden files and folders."
    9. Click Search.

6. Renaming the file and extension
Follow the instructions for your operating system

Windows 95/98/Me
    1. In the search results box, right-click the file that was found > Rename.
    2. Rename the file to Badfile.bad. Click OK or Yes to any warning message.
    3. Close the Find or Search window.

Windows NT/2000/XP
    1. Click Start, and then click Run. (The Run dialog box appears.)
    2. Type, or copy and paste, the following command, and then click OK:

      cmd /c "attrib -h %systemroot%\system32\msconfd.dll & ren %systemroot%\system32\msconfd.dll Badfile.bad"

7. Restarting the computer in Safe mode


WARNING: Do not skip this step. Even though you are in Safe mode, restart the computer to Safe mode a second time. Do not restart to normal mode or the Trojan file will be recreated.

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 ."


8. Deleting the value from 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. 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:

      "Desktop" = "rundll32.exe %System%\msconfd.dll,Restore ControlPanel"

    5. If you are running Windows NT/2000/XP, navigate to the key:

      HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows

    6. In the right pane, delete the value:

      "AppInit_DLLs"="msconfd.dll"

    7. Exit the Registry Editor.

9. Scanning for and deleting the names of the infected files
    1. Start your Symantec antivirus program and run a full system scan.
    2. If any files are detected as infected with Trojan.Bookmarker, click Delete.

10. Resetting the Internet Explorer Home page
    1. Start Microsoft Internet Explorer.
    2. Connect to the Internet and go to the page that you want to set as your home page.
    3. Click Tools, and then click Internet Options.
    4. In the Home page section of the General tab, click Use Current, and then click OK.

11. Resetting the Internet Explorer Search page
Follow the instructions for your version of Windows.

Windows 98/Me/2000
  1. Start Microsoft Internet Explorer.
  2. Click the Search button on the toolbar.
  3. In the Search pane, click Customize.
  4. Click Reset.
  5. Click Autosearch Settings.
  6. Select a search site from the drop-down list, and then click OK.
  7. Click OK.

Windows XP
Because Windows XP is set by default to use animated characters in the search, how you perform this procedure varies. Read all the instructions before you start.
  1. Start Microsoft Internet Explorer.
  2. Click the Search button on the toolbar.
  3. Do one of the following:
    • If the pane that opens looks similar to this picture:




      click the word Customize. Then skip to step h.

    • If the pane that opens has the words "Search Companion" at the top and the center looks similar to this picture:





      click the "Change preferences" link as shown above, Go on to step d.

  4. Click the "Change Internet search behavior" link.
  5. Under "Internet Search Behavior," click "With Classic Internet Search."
  6. Click OK. Then close Internet Explorer. (You must close the program for the change to take effect.)
  7. Start Internet Explorer. When the search pane opens, it should now look similar to this:




    Click the word Customize, and then proceed to the next step.

  8. In the Search pane, click Customize.
  9. Click Reset.
  10. Click Autosearch Settings.
  11. Select a search site from the drop-down list, and then click OK.
  12. Click OK.
  13. Do one of the following:
    • If you were using (or want to continue using) the "Classic Internet Search" panel, skip to section 12.
    • If you want to restore the "Search Companion" search, proceed to step n.

  14. Click the word Customize again.
  15. In the "Customize Search Settings" window, click "Use Search Companion," and then click OK.
  16. Close Internet Explorer. The next time that you open it, it will again use the Search Companion.


12. Removing links added to Favorites
    1. Start Internet Explorer.
    2. Click Favorites, and then Organize Favorites.
    3. Delete the links to the pornographic Web sites that the Trojan inserted.


Writeup By: Yuhui Huang