Trojan.Bookmarker

SUMMARY

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.

Protection

• Virus Definitions (LiveUpdate™ Weekly) December 23, 2003
• Virus Definitions (Intelligent Updater) December 22, 2003

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 50 - 999
• Number of Sites: 3 - 9
• Geographical Distribution: Low
• Threat Containment: Easy
• Removal: Moderate

Damage

• Damage Level: Low

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

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.
   
   

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   Note: %System% is a variable. By default, this is C:WindowsSystem (Windows 95/98/Me), C:WinntSystem32 (Windows NT/2000), or C:WindowsSystem32 (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_MACHINESOFTWAREMicrosoftWindows NTCurrentVersionWindows
   
   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_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   so that the dll is loaded every time you start Windows.
   
   
3. Adds the value:
   
   "Desktop" = "<number>"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionExplorer
   
   

   ---

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

   ---

   
   
4. Creates or overwrites the file, %System%driversetchosts, 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_USERSoftwareMicrosoftInternet ExplorerMain
   
   
6. Adds the value:
   
   "SearchURL"="http:/ /webcoolsearch.com"
   
   to the registry key:
   
   HKEY_CURRENT_USERSoftwareMicrosoftInternet Explorer
   
   
7. Adds the value:
   
   "SearchAssistant"="http:/ /webcoolsearch.com"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftInternet ExplorerSearch
   
   
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":

• Turn off and remove unneeded services. By default, many operating systems install auxiliary services that are not critical, such as an FTP server, telnet, and a Web server. These services are avenues of attack. If they are removed, blended threats have less avenues of attack and you have fewer services to maintain through patch updates.
• If a blended 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 (for example, all Windows-based computers should have the current Service Pack installed.). Additionally, please apply any security updates that are mentioned in this writeup, in trusted Security Bulletins, or on vendor Web sites.
• 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.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread viruses, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate infected computers quickly to prevent further compromising your organization. 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.

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. 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:

• "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. 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

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 Trojan.Bookmarker, write down the file names. Do not try to delete them at this time.

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%system32msconfd.dll & ren %systemroot%system32msconfd.dll Badfile.bad"
   
   

7. Restarting the computer in Safe mode

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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.

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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

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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_MACHINESOFTWAREMicrosoftWindowsCurrentVersion
   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_MACHINESOFTWAREMicrosoftWindows NTCurrentVersionWindows
   
   
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.