Trojan.Bootconf

Trojan.Bootconf is a Trojan Horse that modifies the TCP/IP settings to point to a different DNS server. It will also change your home page and search page in Internet Explorer to connect to out.true-counter.com.

Trojan.Bootconf is written in Microsoft Visual C++.

Also Known As:	Trojan.Qhosts.A, Trojan.Qhosts.B, TrojanClicker.Win32.Qhost.a [KAV]
Type:	Trojan Horse
Infection Length:	varies, known variants are 53,248 or 57,344 bytes
Systems Affected:	Windows 2000, Windows 95, Windows 98, Windows Me, Windows NT, Windows Server 2003, Windows XP
Systems Not Affected:	DOS, Linux, Macintosh, Microsoft IIS, OS/2, UNIX, Windows 3.x

Virus Definitions (Intelligent Updater) * October 13, 2003 Virus Definitions (LiveUpdate™) ** October 15, 2003 * Intelligent Updater definitions are released daily, but require manual download and installation. Click here to download manually. ** LiveUpdate virus definitions are usually released every Wednesday. Click here for instructions on using LiveUpdate.

Wild: Number of infections: 0 - 49 Number of sites: 0 - 2 Geographical distribution: Low Threat containment: Easy Removal: Easy

Threat Metrics Wild: Low Damage: Low Distribution: Low

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

1. Adds the address entry:
   
   <an invalid IP address> auto.search.msn.com
   
   to the HOSTS file, disabling access to this site.
   
   
2. Creates a non-viral file in different locations, depending on the variant. Known variants have installed this file in %Windir%\Web\Oslogo.bmp and %Windir%\default.css.
   
   

   ---

   Note: %Windir% is a variable. The Trojan locates the Windows installation folder (by default, this is C:\Windows or C:\Winnt), and creates a file in that directory or in a subdirectory.

   ---

   
   
3. Adds the values:
   
   • "Search" = <encoded URL>
   • "SearchURL" = <encoded URL>
     
     in the registry key:
     
     HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer
     
     The URL varies, and may be one of:
     
   • http:// %6f%75%74%2e%74%72%75%65%2d%63%6f%75%6e%74%65%72%2e%63%6f%6d/%61/?%33%34%34%30%31%32
     (out.true-counter.com)
   • http:// %77%77%77%2e%63%6f%6f%6c%77%77%77%73%65%61%72%63%68%2e%63%6f%6d/%7a/%61/%78%31%2e%63%67%69?%33%34%34%30%31%32
     (www.coolwwwsearch.com/z/a/x1.cgi)
     
     
4. Adds the values:
   
   • "SearchAssistant" = <encoded URL>
   • "CustomizeSearch" = <encoded URL>
     
     in the registry key:
     
     HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Search
     
     
5. Modifies the values:
   
   • "Search Page" = <encoded URL>
   • "Default_Search_URL" = <encoded URL>
   • "Search Bar" = <encoded URL>
   • "Default_Page_URL" = <encoded URL>
   • "Start Page" = <encoded URL>
     
     in the registry key:
     
     HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
     
     
6. Modifies the values:
   
   • "User Stylesheet" = <the filename from step #2>
   • "Use My Stylesheet" = "1"
     
     in the registry key:
     
     HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Styles

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.
• 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.

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 or VGA mode.
4. Run a full system scan and delete all the files detected as Trojan.Bootconf.
5. Delete the value that was added to the registry.
6. Restore Internet Explorer settings.
   

• "How to disable or enable Windows Me System Restore"
• "How to turn off or turn on Windows XP System Restore"
  

• 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.

• For Windows 95, 98, Me, 2000, or XP users, restart the computer in Safe mode. For instructions, read the document, "How to start the computer in Safe Mode."
• For Windows NT 4 users, restart the computer in VGA mode.

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.Bootconf, click Delete.

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_CURRENT_USER\Software\Microsoft\Internet Explorer
   
   
4. In the right pane, delete the values:
   
   • "Search" = <encoded URL>
   • "SearchURL" = <encoded URL>
     
     
5. Navigate to the key:
   
   HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Search
   
   
6. In the right pane, delete the values:
   
   • "SearchAssistant" = <encoded URL>
   • "CustomizeSearch" = <encoded URL>
     
     
7. Exit the Registry Editor.

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.

Revision History:

• October 15, 2003: Renamed to Trojan.Bootconf from Trojan.Qhosts.B.
• October 14, 2003: Renamed to Trojan.Qhosts.B from Trojan.Qhosts.A.

Write-up by: Hiroshi Shinotsuka