W32.Hostidel.Trojan

SUMMARY

W32.Hostidel.Trojan is a Trojan horse that overwrites the Windows Hosts files, which are used for name resolution.

This Trojan also modifies the Windows registry to change the Internet Explorer home page and the default search page in Internet Explorer.

Protection

• Virus Definitions (LiveUpdate™ Weekly) November 13, 2003
• Virus Definitions (Intelligent Updater) November 13, 2003

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 0 - 49
• Number of Sites: 0 - 2
• Geographical Distribution: Low
• Threat Containment: Easy
• Removal: Easy

Damage

• Damage Level: Low
• Payload Trigger: N/A
• Payload: N/A
• Large Scale E-mailing: N/A
• Deletes Files: N/A
• Modifies Files: N/A
• Releases Confidential Info: N/A
• Degrades Performance: N/A
• Causes System Instability: N/A
• Compromises Security Settings: Changes the Internet Explorer settings.

Distribution

• Distribution Level: Low
• Subject of Email: N/A
• Name of Attachment: N/A
• Size of Attachment: N/A
• Ports: N/A
• Shared Drives: N/A
• Target of Infection: N/A
• Time Stamp of Attachment: N/A

TECHNICAL DETAILS

When W32.Hostidel.Trojan is executed, it performs the following actions:

1. Creates the following URL entries:
   • %Favorites%Horny And Drunk - Best Hardcore Porn.url
   • %Favorites%Free Family Porn - Forbidden Incest Pics and Videos.url
   • %Favorites%XXX HQ-PICS ARCHIVE.url
   • %Favorites%Incest Hardcore For Free.url
   • %Favorites%Cheap travels here.url
   • %Favorites%Home loan search.url
   • %Favorites%PERFECT SEARCH.url
     
     

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     Note: %Favorites% is a variable. The Trojan locates the Favorites folder by querying HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionExplorerShell FoldersFavorites in the Windows registry.

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2. Searches for the Windows host file in the following locations:
   
   • %Windir%hosts
   • %System%driversetchosts
     
     

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     Notes:
     
     %Windir% is a variable. By default, this is C:Windows or C:Winnt.
     
     %System% is a variable. By default, this is C:WindowsSystem (Windows 95/98/Me), C:WinntSystem32 (Windows NT/2000), or C:WindowsSystem32 (Windows XP).
     

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3. Deletes all the entries from the Hosts files it finds, and then writes the following entries to those files:
   
   • 127.0.0.1     localhost
   • 66.250.107.99     thehun.net
   • 66.250.107.99     www.thehun.net
   • 66.250.107.99     thehun.com
   • 66.250.107.99     www.thehun.com
   • 66.250.107.99     worldsex.com
   • 66.250.107.99     www.worldsex.com
   • 66.250.107.99     sexocean.com
   • 66.250.107.99     www.sexocean.com
   • 66.250.107.99     easypic.com
   • 66.250.107.99     www.easypic.com
   • 66.250.107.99     free6.com
   • 66.250.107.99     www.free6.com
   • 66.250.107.99     al4a.com
   • 66.250.107.99     www.al4a.com
   • 66.250.107.99     thumbnailpost.com
   • 66.250.107.99     www.thumbnailpost.com
   • 66.250.107.99     drbizzaro.com
   • 66.250.107.99     www.drbizzaro.com
   • 66.250.107.99     hoes.com
   • 66.250.107.99     www.hoes.com
   • 66.250.107.99     absolut-series.com
   • 66.250.107.99     www.absolut-series.com
   • 66.250.107.99     elephantlist.com
   • 66.250.107.99     www.elephantlist.com
   • 66.250.107.99     ah-me.com
   • 66.250.107.99     www.ah-me.com
   • 66.250.107.100    msn.com
   • 66.250.107.100    www.msn.com
   • 66.250.107.100    search.msn.com
   • 66.250.107.100    auto.search.msn.com
   • 66.250.107.101    google.com
   • 66.250.107.101    google.de
   • 66.250.107.101    google.co.in
   • 66.250.107.101    google.ca
   • 66.250.107.101    google.fr
   • 66.250.107.101    google.it
   • 66.250.107.101    google.com.au
   • 66.250.107.101    google.co.uk
   • 66.250.107.101    google.be
   • 66.250.107.101    google.com.ar
   • 66.250.107.101    www.google.com
     
     
4. Adds the value:
   
   "SearchAssistant"="http:/ /www.find-itnow.com/panel_search.html"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftInternet ExplorerSearch
   
   
5. Adds the values:
   
   "(Default)"="http:/ /www.find-itnow.com/search.html"
   "provider"="god"
   
   to the registry key:
   
   HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerSearchURL
   
   
6. Adds the values:
   
   "Start Page"="http:/ /www.find-itnow.com/search.html"
   "Use Search Asst"="no"
   "Search Page"="http:/ /www.find-itnow.com/search.html"
   "Search Bar"="http:/ /www.find-itnow.com/panel_search.html"
   
   to the registry key:
   
   HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerMain

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 delete all the files detected asW32.Hostidel.Trojan. Manually delete the files added to the Favorites folder.
4. Reset the Internet Explorer search defaults.
5. Delete the values that were added to the registry.
6. Restore the Hosts file.
   

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 deleting 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 W32.Hostidel.Trojan, click Delete.
4. Using Windows explorer, locate and delete these files:
   • %Favorites%Horny And Drunk - Best Hardcore Porn.url
   • %Favorites%Free Family Porn - Forbidden Incest Pics and Videos.url
   • %Favorites%XXX HQ-PICS ARCHIVE.url
   • %Favorites%Incest Hardcore For Free.url
   • %Favorites%Cheap travels here.url
   • %Favorites%Home loan search.url
   • %Favorites%PERFECT SEARCH.url

4. Resetting the Internet Explorer search defaults

1. Start Internet Explorer.
   
2. On the Tools menu, click Internet Options.
   
3. On the Internet Options dialog box, click the Programs tab.
   
4. Click Reset Web Settings, and then click Yes to Confirm.
   
5. Click OK.

5. Deleting the values 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_CURRENT_USERSoftwareMicrosoftInternet ExplorerSearchURL
   
   
4. In the right pane, delete the value:
   
   "(Default)"="http:/ /www.find-itnow.com/search.html"
   
   
5. Navigate to the key:
   
   HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerMain
   
   
6. In the right pane, delete the values:
   
   "Use Search Asst"="no"
   "Search Bar"="http:/ /www.find-itnow.com/panel_search.html"
   
   
7. Exit the Registry Editor.
   

6. Restoring the Hosts file

1. Using Windows Explorer, look for the Windows host file in the following locations, if they exist:
   • %Windir%hosts
   • %System%driversetchosts
     
     
2. For each Hosts file you find, double-click the file.
3. When the "Open With" dialog box appears, scroll through the list and select Notepad. Do not check the "Always open this program with. . ." box.
4. Within the file, delete all the entries in the Hosts file except for the following line:
   
   127.0.0.1     localhost
   
   
5. Save the Hosts file.