Discovered: October 01, 2003
Updated: February 13, 2007 12:08:26 PM
Also Known As: QHosts-1 [McAfee], VBS.QHOSTS [CA], Troj/Qhosts-1 [Sophos], TROJ_QHOSTS.A [Trend], Trojan.BAT.Delude.c [KAV]
Type: Trojan Horse
Systems Affected: Windows
CVE References: CAN-2003-0532


Trojan.Qhosts is a Trojan Horse that will modify the TCP/IP settings to point to a different DNS server.

Trojan.Qhosts cannot spread by itself. The user must open an HTML page that contains malicious code, which allows the Trojan to open a viral HTML file on the target computer so that the script can create and run the malicious executable.

Symantec Security Response has received reports that visiting a specific page on www.fortunecity.com caused a popup to be displayed, which redirected the visitor to a different Web page. Being redirected to the Web page appears to have caused the Trojan Horse to be downloaded to a visitor's system, and then executed. Reports also state that the threat exploited the Internet Explorer Object Data Remote Execution vulnerability on several victims' computers to execute itself. Microsoft has released a cumulative patch for this vulnerability.


Antivirus Protection Dates

  • Initial Rapid Release version October 02, 2003
  • Latest Rapid Release version August 13, 2018 revision 034
  • Initial Daily Certified version October 02, 2003 revision 002
  • Latest Daily Certified version August 14, 2018 revision 006
  • Initial Weekly Certified release date October 02, 2003

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

Writeup By: Douglas Knowles

Discovered: October 01, 2003
Updated: February 13, 2007 12:08:26 PM
Also Known As: QHosts-1 [McAfee], VBS.QHOSTS [CA], Troj/Qhosts-1 [Sophos], TROJ_QHOSTS.A [Trend], Trojan.BAT.Delude.c [KAV]
Type: Trojan Horse
Systems Affected: Windows
CVE References: CAN-2003-0532


When the Trojan.Qhosts HTML file is opened, it performs the following actions:

  1. Creates the file %System%\Aolfix.exe.

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

  2. Executes the Aolfix.exe file, which then performs the following actions:

    • Creates the hidden folder C:\Bdtmp\Tmp.
    • Creates and runs the batch file C:\Bdtmp\Tmp\[RANDOM NUMBER BETWEEN 100 AND 9999].bat.
    • Deletes the C:\Bdtmp\Tmp\[RANDOM NUMBER BETWEEN 100 AND 9999].bat file.
    • Deletes the file aolfix.exe.

  3. Creates and executes the following files:

    • %Windir%\o.reg
    • %Windir%\o2.reg
    • %Windir%\o.vbs

      Note: %Windir% is a variable that refers to the Windows installation folder. By default, this is C:\Windows or C:\Winnt.

  4. Adds the values:

    "EnableDNS" = "1"
    "NameServer" = "[IP address(es) specified in the batch file]"
    "HostName" = "host"
    "Domain" = "mydomain.com"

    to the registry subkey:

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\VxD\MSTCP

    so that the DNS server is redirected to one that the Trojan's creator specified.

  5. Adds the values:

    "ProxyEnable" = "0"
    "MigrateProxy" = "0"

    to the registry key:

    HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\
    Internet Settings

  6. Adds the values:

    "Use Search Asst" = "no"
    "Search Page" = ["http://]www.google.com/[REMOVED]/"
    "Search Bar" = "[http://]www.google.com/[REMOVED]/ie"

    to the registry key:

    HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main

    to redirect the Internet Explorer search pages.

  7. Adds the value:

    "" = "[http://]www.google.com/[REMOVED]/keyword/%%s"
    "provider" = "gogl"

    to the registry key:

    HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\SearchURL

    to redirect the Internet Explorer search pages.

  8. Adds the value:

    "SearchAssistant" = "[http://]www.google.com/[REMOVED]/ie"

    to the registry key:

    HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Search

    to redirect the Internet Explorer search pages.

  9. Adds the value:

    "DataBasePath" = "%SystemRoot%\help"

    to the registry key:

    HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Tcpip\
    Parameters
    HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Services\Tcpip\
    Parameters

  10. Adds the value:

    "r0x" = "your s0x"

    to the registry keys:

    HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Tcpip\
    Parameters\Interfaces\Windows
    HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Services\Tcpip\
    Parameters\Interfaces\Windows

  11. Sets a string value for all of the subkeys of the following registry keys:

    HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Tcpip\
    Parameters\Interfaces
    HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Services\Tcpip\
    Parameters\Interfaces

    of:

    "NameServer" = "[IP address(es) specified in the batch file]"

  12. Creates the following file %Windir%\System\winlogon.exe.

  13. May add itself as as service by adding the following registry key

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\nwclnte

  14. Modifies the Hosts file to redirect many different URLs to an IP address specified by the author.

  15. Attempts to delete the following services from the service control manager database:

    • nwclnta
    • nwclntmon
    • nwclnt
    • wuauserv
    • navapsvc
    • Symantec Core LC
    • SAVScan
    • kavsvc

      Note: The above services relate to Security products and Windows updates.



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: Douglas Knowles

Discovered: October 01, 2003
Updated: February 13, 2007 12:08:26 PM
Also Known As: QHosts-1 [McAfee], VBS.QHOSTS [CA], Troj/Qhosts-1 [Sophos], TROJ_QHOSTS.A [Trend], Trojan.BAT.Delude.c [KAV]
Type: Trojan Horse
Systems Affected: Windows
CVE References: CAN-2003-0532


Removal using the Trojan.Qhosts Removal Tool
Symantec Security Response has developed a removal tool to clean the infections of Trojan.Qhosts. This is the easiest way to remove this threat and should be tried first.

Manual 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. Remove all the entries that the risk added to the hosts file.
  3. Reinstall your Symantec antivirus program.
  4. Update the virus definitions.
  5. Run a full system scan and delete all the files detected.
  6. Delete any values added to the registry.
  7. Reset the Internet Explorer search page.
  8. Extract and restore Windows files.
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:
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 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%\System32\drivers\etc

      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.

3. To reinstall your Symantec antivirus program
As this risk attempts to remove the files and registry subkeys that your Symantec antivirus program uses, you may need to reinstall the program. If your Symantec antivirus program is not working properly, uninstall, and then reinstall it.

4. 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 document: 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 the document: 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.


5. 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, 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.


6. 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 the subkey:

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\VxD\MSTCP

    Note: This key may not exist on Windows XP computers.

  5. In the right pane, delete the values:

    "EnableDNS" = "1"
    "NameServer" = "[IP address specified in the batch file]"
    "HostName" = "host"
    "Domain" = "mydomain.com"

  6. Navigate to the subkey:

    HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings

  7. In the right pane, delete the values:

    "ProxyEnable"="0"
    "MigrateProxy"="0"

  8. Navigate to the keys:

    HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Tcpip\Parameters\
    Interfaces\Windows
    HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Services\Tcpip\Parameters\
    Interfaces\Windows

  9. In the right pane, delete the value:

    "r0x" = "your s0x"

  10. Navigate to the keys:

    HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Tcpip\Parameters
    HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Services\Tcpip\Parameters

  11. Modify the value:

    "DataBasePath" = "%SystemRoot%\help"

    to:

    "DataBasePath" = "%SystemRoot%\System32\drivers\etc"

  12. Navigate to the keys:

    HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Tcpip\Parameters\
    Interfaces
    HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Services\Tcpip\Parameters\
    Interfaces

  13. For each subkey, restore the value:

    "NameServer" = "[IP address specified in the batch file]"

    Note: The default for many configurations is an empty string.

  14. Exit the registry Editor.

7. 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.

8. To reinstall Windows Automatic Update
The threat deletes a service relating to Windows Automatic Update. As a result of this it may be necessary to reinstall Automatic Update. The following document provides general instructions on how to do this. This information is provided for your convenience. The exact steps may vary slightly depending on the configuration of your operation system, the location of the files, and so on. For additional information, read the Help files, contact Microsoft, or refer to the following Windows documentation:

The Microsoft Knowledge Base article: Procedure to manually Re-Install Automatic Update Client for Windows Server Updates Services, WSUS .



Writeup By: Douglas Knowles