W32.Hostidel.Trojan.B - 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 as W32.Hostidel.Trojan.B.
4. Reset the Internet Explorer search defaults and manually delete the files added to the Favorites folder.
5. Delete the values that were added to the registry.
6. Reverse the changes made to 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.B, click Delete.

4. Resetting the Internet Explorer defaults, manually deleting the files added to the Favorites folder

1. Start Internet Explorer.
2. Click the Tools menu, and then click Internet Options.
3. Click the Programs tab.
4. Click Reset Web Settings, and then click Yes to confirm.
5. Click OK.
6. Click the Favorites menu, and then click Organize Favorites.
7. Remove the entries listed in step 3 of the "Technical Details" section.

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_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
   
   
4. In the right pane, delete the value:
   
   "Online Service"="%Windir%\svchost.exe..."
   
   
5. Navigate to the key:
   
   HKEY_LOCAL_MACHINE\Software\Microsoft\Mserv
   
   
6. In the right pane, delete the value:
   
   "IDwin"="002000112003000000490033"
   
   
7. Exit the Registry Editor.
   

6. Reversing the changes made to the Hosts file
The Hosts file is not found on all the computers, and if it does exist, the location can vary. For example, if the file exists in Windows 98, it will usually be in C:\Windows; and in Windows 2000, it is in the C:\WINNT\SYSTEM32\DRIVERS\ETC folder. Also, there may be multiple copies of this file in different locations.

The most efficient way to locate the file is to search for it.

Follow the instructions for your operating system:

• Windows 95/98/Me/NT/2000
  1. Click Start, point to Find or Search, and then click Files or Folders.
  2. Make sure that "Look in" is set to (C:) and that "Include subfolders" is checked.
  3. In the "Named" or "Search for..." box, type:
     
     hosts
     
     
  4. Click Find Now or Search Now.
  5. For each one that you find, note its location. (This is displayed in the "In Folder" column.)
  6. If any of the files that are found have a path that includes:
     
     \drivers\etc\hosts
     
     right-click the file, and then click "Open With."
     
     
  7. Deselect the "Always use this program to open this program" check box.
  8. Scroll through the list of programs and double-click Notepad.
  9. When the file opens, within the file, delete all the entries in the Hosts file, except for the following line:
     
     127.0.0.1     localhost
     
     
  10. Close Notepad and save your changes when prompted.
      
      
• Windows XP
  1. Click Start, and then click Search.
  2. Click All files and folders.
  3. In the "All or part of the file name" box, type:
     
     hosts
     
     
  4. Verify that "Look in" is set to "Local Hard Drives" or to (C:).
  5. Click "More advanced options."
  6. Check "Search system folders."
  7. Check "Search subfolders."
  8. Click Search.
  9. Click Find Now or Search Now
  10. For each one that you find, note its location. (This is displayed in the "In Folder" column.)
  11. If any of the files that are found have a path that includes:
      
      \drivers\etc\hosts
      
      right-click the file, and then click "Open With."
      
      
  12. Deselect the "Always use this program to open this program" check box.
  13. Scroll through the list of programs and double-click Notepad.
  14. When the file opens within the file, delete all the entries in the Hosts file except for the following line:
      
      127.0.0.1     localhost
      
      
  15. Close Notepad and save your changes when prompted.
      

Technical Details