W32.HLLW.Backzat.G - Removal

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

NOTE: If the worm has run and succeeded to delete your Symantec antivirus product, re-install it before you can scan for and delete the
worm. In this situation, first follow the instructions in the "Reversing the changes made to the registry" section, restart the computer, and then re-install your antivirus product.

1. Update the virus definitions.
2. Run a full system scan and delete all the files detected as W32.HLLW.Backzat.G. Restore any required files, which the worm overwrote, from a clean backup. Manually delete the files:
   • C:\%windir%\Kirbybmp.bmp.
   • C:\%windir%\KirbyWins.mp3
3. Reverse the changes made to the registry.

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.HLLW.Backzat.G, write down the file names, and then click Delete.
4. Using Windows Explorer, locate and delete the files:
   • C:\%windir%\Kirbybmp.bmp.
   • C:\%windir%\KirbyWins.mp3
     

3. Reversing the changes made to the registry

CAUTION: Symantec 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, and then click OK. (The Registry Editor opens.)
3. Navigate to the registry key:
   
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
   
   In the right pane, delete this value:
   
   WinSysStartUpWKbLw C:\%system%\TaskSystemDll.Exe
   
4. Navigate to the registry key:
   
   HKEY_CURRENT_USER\Control Panel\Desktop
   
   In the right pane, delete this value:
   
   SCRNSAVE.EXE C:\%system%\CuteKirby.Scr
   
   Next, double-click wallpaper
   
   and delete the text:
   
   C:\%windir%\Kirbybmp.bmp
   
   from the Value Data box.
   
5. Click Registry, and then click Exit.

Technical Details