Trojan.StartPage

SUMMARY

Trojan.StartPage is a Trojan horse that modifies the Internet Explorer home page without authorization.

Protection

• Virus Definitions (LiveUpdate™ Weekly) January 16, 2002
• Virus Definitions (Intelligent Updater) January 15, 2002

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: More than 1000
• Number of Sites: More than 10
• Geographical Distribution: High
• Threat Containment: Easy
• Removal: Moderate

Damage

• Damage Level: Low
• Payload: Modifies settings in Internet Explorer.

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

When Trojan.StartPage is executed, it performs the following actions:

1. Copies itself to the %System% or the %Windir% folder with a variable file name.
   
   
   Note:
   • %System% is a variable. The Trojan locates the System folder and copies itself to that location. By default, this is C:WindowsSystem (Windows 95/98/Me), C:WinntSystem32 (Windows NT/2000), or C:WindowsSystem32 (Windows XP).
   • %Windir% is a variable. The Trojan locates the Windows installation folder (by default, this is C:Windows or C:Winnt) and copies itself to that location.
   • The file names vary and are often selected to resemble the names of legitimate Windows system files. Some examples include Rundll32.exe and winproc32.exe. However, other file names have been seen.
     
     
2. Adds a value in the form:
   
   "[VALUE]" = "[TROJAN FILE NAME]"
   
   to one or both of the registry subkeys:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   HKEY_CURRENT_USERSOFTWAREMicrosoftWindowsCurrentVersionRun
   
   so that the Trojan runs when you start Windows.
   
   The values may be one of the following:
   
   "Windows Internet Protocol" = "%System%winproc32.exe "
   "rundll32" = "%System%undll32.exe"
   "SysSearch" = "REGEDIT.EXE -s %Windir%sysreg.reg"
   "sp" = "rundll32 %Temp%se.dll,DllInstall"
   
   These values may be recreated periodically.
   
   
3. May drop an auxiliary data file into the %Windir%, %Temp%, or %System% folder.
   
   Note: %Temp% is a variable that refers to the Windows temporary folder. By default, this is C:WindowsTEMP (Windows 95/98/Me/XP) or C:WINNTTemp (Windows NT/2000).
   
   
4. May add entries to %Windir%hosts or %System%driversetchosts file, to redirect access to certain Web sites.
   
   
5. May change settings in Internet Explorer by modifying the following subkeys:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftInternet ExplorerMainStartPage
   HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerMainSearch Page
   HKEY_LOCAL_MACHINESoftwareMicrosoftInternet ExplorerMainSearch Page
   HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerMainSearch Bar
   HKEY_LOCAL_MACHINESoftwareMicrosoftInternet ExplorerMainSearch Bar
   HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerSearchUrl
   HKEY_LOCAL_MACHINESoftwareMicrosoftInternet ExplorerSearchUrl
   HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerSearch
   HKEY_LOCAL_MACHINESoftwareMicrosoftInternet ExplorerSearch
   HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerTypedUrls
   HKEY_LOCAL_MACHINESoftwareMicrosoftInternet ExplorerUse Search Asst
   HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerUse Search Asst
   HKEY_LOCAL_MACHINESoftwareMicrosoftInternet ExplorerUse Custom Search URL
   HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerUse Custom Search URL
   HKEY_LOCAL_MACHINESoftwareMicrosoftInternet ExplorerDefault_Search_URL
   HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerDefault_Search_URL
   HKEY_LOCAL_MACHINESoftwareMicrosoftInternet ExplorerSearchAssistant
   HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerSearchAssistant
   HKEY_LOCAL_MACHINESoftwareMicrosoftInternet ExplorerCustomizeSearch
   HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerCustomizeSearch
   
   
6. May add a list of URLs to the Favorites folder, some of which may contain adult content.
   
   
7. May add itself as a Browser Helper Object by creating the following subkey:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionExplorerBrowser Helper Objects{[RANDOM CLSID]}
   
   Note: [RANDOM CLSID] is a random value in the form {########-####-####-####-############}. For example {B4E9FAC4-6DB5-4741-84C9-97923F6D5976}.
   

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. Close all open Internet Explorer windows.
3. Remove all the entries that the risk added to the hosts file .
4. End the malicious process. (Windows NT/2000/XP).
5. Update the virus definitions.
6. Run a full system scan and delete all the files detected.
7. Delete any values added to the registry.
8. Reset the Internet Explorer home page.
9. Reset the Internet Explorer search page.
10. Delete the Web sites added to the Internet Explorer Favorites menu.
    

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 close all open Internet Explorer windows
Because Trojan.Startpage may function as a Microsoft Internet Explorer plugin, it is necessary to close all open Internet Explorer windows to remove it. If you are reading this writeup in Internet Explorer, print this writeup using our printer-friendly option at the top of the page, or write down the following instructions, and then close all Internet Explorer windows.

3. To remove all the entries that the risk added to the hosts file

1. Navigate to the following location:
   
   
   • Windows 95/98/Me:
     %Windir%
   • Windows NT/2000/XP:
     %Windir%System32driversetc
     
     Notes:
   • The location of the hosts file may vary and some computers may not have this file. There may also be multiple copies of this file in different locations. If the file is not located in these folders, search your disk drives for the hosts file, and then complete the following steps for each instance found.
   • %Windir% is a variable that refers to the Windows installation folder. By default, this is C:Windows (Windows 95/98/Me/XP) or C:Winnt (Windows NT/2000).
     
     
2. Double-click the hosts file.
3. If necessary, deselect the "Always use this program to open this program" check box.
4. Scroll through the list of programs and double-click Notepad.
5. When the file opens, delete all the entries in the Hosts file, except for the following line:
   
   127.0.0.1     localhost
   
6. Close Notepad and save your changes when prompted.

4. To end the malicious process. (Windows NT/2000/XP)

To end the malicious process:
1. Press Ctrl+Alt+Delete once.
2. Click Task Manager.
3. Click the Processes tab.
4. Double-click the Image Name column header to alphabetically sort the processes.
5. Scroll through the list and look for rundll32.exe and regsvr32.exe.
6. If you find the file, click it, and then click End Process.
7. Exit the Task Manager.
   

5. 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.

6. 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.

Important: If you are unable to start your Symantec antivirus product or the product reports that it cannot delete a detected file, you may need to stop the risk from running in order to remove it. To do this, run the scan in Safe mode. For instructions, read the document, How to start the computer in Safe Mode. Once you have restarted in Safe mode, run the scan again.

After the files are deleted, restart the computer in Normal mode and proceed with the next section.

Warning messages may be displayed when the computer is restarted, since the threat may not be fully removed at this point. You can ignore these messages and click OK. These messages will not appear when the computer is restarted after the removal instructions have been fully completed. The messages displayed may be similar to the following:

Title: [FILE PATH]
Message body: Windows cannot find [FILE NAME]. Make sure you typed the name correctly, and then try again. To search for a file, click the Start button, and then click Search.


7. To delete the value from 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 each of these subkeys:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   HKEY_CURRENT_USERSOFTWAREMicrosoftWindowsCurrentVersionRun
   
   
5. In the right pane, delete any values that refer to the files detected.
   
   
6. Navigate to, and delete each of the following subkeys:
   
   HEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionExplorer
   Browser Helper Objects{0B6F9689-431B-4631-85CB-3CF087ECEDBD}
   HKEY_CLASSES_ROOTCLSID{0B6F9689-431B-4631-85CB-3CF087ECEDBD}
   HKEY_LOCAL_MACHINESOFTWAREClassesCLSID
   {0B6F9689-431B-4631-85CB-3CF087ECEDBD}
   HKEY_CLASSES_ROOTCLSID{B4E9FAC4-6DB5-4741-84C9-97923F6D5976}
   HKEY_LOCAL_MACHINESOFTWAREClassesCLSID
   {B4E9FAC4-6DB5-4741-84C9-97923F6D5976}
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersion
   UninstallSearchAssistant Uninstall
   
   
7. Navigate to each of these registry subkeys:
   
   HKEY_LOCAL_MACHINESOFTWAREClassesPROTOCOLSFilter ext/plain
   HKEY_LOCAL_MACHINESOFTWAREClassesPROTOCOLSFilter ext/html
   HKEY_CLASSES_ROOTPROTOCOLSFilter ext/plain
   HKEY_CLASSES_ROOTPROTOCOLSFilter ext/html
   
   
8. In the right pane, delete the following value:
   
   "CLSID" = "{B4E9FAC4-6DB5-4741-84C9-97923F6D5976}"
   
   
9. Exit the Registry Editor.

8. To reset the Internet Explorer home page

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

For additional information, or if this procedure does not work, read the Microsoft® Knowledge Base article: Home Page Setting Changes Unexpectedly, or You Cannot Change Your Home Page Setting, Article ID 320159.

9. To reset 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 do this can vary. 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 the following picture, click the word Customize and proceed to step h:
     
     
     
     
     
   • If the pane that opens has the words "Search Companion" at the top, and the center looks similar to the following picture, click the Change preferences link and proceed with 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. (Close the program for the change to take effect.)
7. Start Internet Explorer. When the search pane opens, it should look similar to the following picture:
   
   
   
   
   
   Click the word Customize, and then proceed with 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, stop here (or proceed with the next section).
    • If you want to go back to the "Search Companion" search (it usually has an animated character at the button), proceed with step n.
      
      
14. Click the word Customize again.
15. In the "Customize Search Settings" window, click Use Search Companion > OK.
16. Close Internet Explorer. The next time you open it, it will again use the Search Companion.

10. To delete the Web sites added to the Internet Explorer Favorites menu

1. Start Microsoft Internet Explorer
2. Click Favorites > Organize Favorites
3. Delete the Favorites added by the risk