W32.HLLW.Kullan - Removal

Once this type of threat attacks a computer, it is difficult to determine what else the computer has been exposed to.

In most cases, changes—other than those made by this threat—will not have occurred. However, a hacker may have been able to use the threat to access the computer to make changes to it.

Unless you can be absolutely sure that malicious activity has not been performed on the computer, we recommend completely re-installing the operating system.

If you are on a network or have a full-time connection to the Internet, disconnect the computer from the network and the Internet. Disable or password-protect file sharing before reconnecting the computers to the network or to the Internet. Because this worm spreads by using shared folders on networked computers, to ensure that the worm does not re-infect the computer after it has been removed, Symantec suggests sharing with read only access or using password protection. For instructions, see your Windows documentation or the document, "How to configure shared Windows folders for maximum network protection."

IMPORTANT: Do not skip this step. Disconnect from the network before attempting to remove this worm.

The following 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 the files detected as W32.HLLW.Kullan.
3. Reverse the changes that were made to the registry.
4. Reverse the changes that were made to the Win.ini and System.ini files (Windows 95/98/Me).
   

For specific details on each of these steps, 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 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 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.HLLW.Kullan, write down the filenames, and then click Delete.

3. Reversing the changes that were made to 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, and then click Run. (The Run dialog box appears.)
   
   
2. Type regedit
   
   Then click OK. (The Registry Editor opens.)
   
   
3. Navigate to the keys:
   
   HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\
   Windows\Load
   HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\
   Windows\Run
   HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
   HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
   
   
   
4. For each one, in the right pane, delete any values that refer to the files detected as W32.HLLW.Kullan.
   
   
5. Navigate to the keys:
   
   HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Winlogon
   HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Winlogon
   
   
6. For each one, in the right pane, look for the value:
   
   "shell"="Explorer.exe <file name>.exe
   
   where <file name> refers to a file detected as W32.HLLW.Kullan.
   
   
7. If this data exists, delete everything to the right of Explorer.exe.
   
   When you are done, it should look like:
   
   Explorer.exe
   
   
8. Exit the Registry Editor.

4. Editing Win.ini and System.ini
If you are running Windows 95/98/Me, follow these steps:

1. The function 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 need to edit. If this backup copy exists, it will be in the C:\Windows\Recent folder. Symantec recommends that you delete this file before continuing with the steps in this section. To do this:
     1. Start Windows Explorer.
     2. Browse to and select the C:\Windows\Recent folder.
     3. In the right pane, select the Win.ini file and delete it. The Win.ini file will be regenerated when you save your changes to it in step f.
        
        
        
2. Click Start, and then click Run.
   
   
3. 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.
   
   
4. Look for a line similar to:
   
   load = Explorer.exe <file name>.exe
   
   or:
   
   run = Explorer.exe <file name>.exe
   
   
5. If either line exists, delete the entire line.
   
   
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\system.ini
   
   (The MS-DOS Editor opens.)
   
   NOTE: If Windows is installed in a different location, make the appropriate path substitution.
   
   
10. In the [boot] section, look for a line similar to:
    
    shell = Explorer.exe <file name>.exe
    
    
11. If this line exists, delete everything to the right of Explorer.exe.
    
    When you are done, it should look like:
    
    shell = Explorer.exe
    
    
12. Click File, and then click Save.
    
    
13. Click File, and then click Exit.

Technical Details