W32.Yalat.Worm - Removal

These instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

1. Update the virus definitions.
2. Run a full system scan, and delete all files that are detected as W32.Yalat.Worm.
3. Delete the value:
   
   WinHaelp.exe %Windows%\WinHaelp.exe
   
   from the registry key:
   
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\
   CurrentVersion\RunServices
   
4. Reverse the changes that the worm made to the Win.ini and System.ini files.
   

For specific details on each of these procedures, read the following instructions.

1. 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 the 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), in the "Protection" section, at the top of this writeup.
• 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), in the "Protection" section, at the top of this writeup.
  
  The Intelligent Updater virus definitions are available here. For detailed instructions on how to download and install the Intelligent Updater virus definitions from the Symantec Security Response Web site, click here.

2. 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.Yalat.Worm, click Delete.

3. Deleting the value from the registry

CAUTION: Symantec strongly recommends that you back up the registry before you make 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.

1. Click Start then click Run. (The Run dialog box appears.)
2. Type regedit and then click OK. (The Registry Editor opens.)
3. Navigate to the key:
   
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\
   CurrentVersion\RunServices
   
   NOTE: This key does not exist on all operating systems
   
4. In the right pane, delete the value:
   
   WinHaelp.exe %Windows%\WinHaelp.exe
   
5. Exit the Registry Editor.

4. Reversing the changes that the worm made to the Win.ini and System.ini files.

If you are running Windows 95/98/Me, follow these steps:

1. The function that you perform depends on your operating system:
   • Windows 95/98: Go to step b.
   • Windows Me: If you are running Windows Me, the Windows Me file-protection process may have made a backup copy of the Win.ini file that you are to edit. If this backup copy exists, it will be in the C:\Windows\Recent folder. Symantec recommends that you delete this file before you continue with the steps in this section. To do this:
     • Start Windows Explorer.
     • Browse to and select the C:\Windows\Recent folder.
     • In the right pane, select the Win.ini and System.ini files and delete them.. They will be regenerated when you save your changes to them in steps f and m.
       
2. Click Start, and then click Run.
3. Type the following, and then click OK.
   
   edit c:\windows\system.ini
   
   (The MS-DOS Editor opens.)
   
   NOTE: If Windows is installed in a different location, make the appropriate path substitution.
   
4. In the [boot] section of the file, look for a line that is similar to the following:
   
   shell=Explorer.exe WinHaelp.exe
   
5. If it exists, delete everything to the right of Explorer.exe.
   
   When you have finished, it should look like:
   
   shell=Explorer.exe
   
6. Click File, and then click Save.
7. Click File, and then click Exit.
8. Click Start, and then click Run.
9. Type the following, and then click OK.
   
   edit c:\windows\win.ini
   
   (The MS-DOS Editor opens.)
   
   NOTE: If Windows is installed in a different location, make the appropriate path substitution.
   
10. Look for a line that is similar to the following:
    
    load=WinHaelp.exe
    
11. If it exists, delete the entire line.
12. Click File, and then click Save.
13. Click File, and then click Exit.

Technical Details