W32.HLLW.Backzat.G

SUMMARY

W32.HLLW.Backzat.G is a mass-mailing worm that uses Microsoft Outlook to send itself to all the contacts in the Microsoft Outlook Address Book. It also attempts to spread itself through the Grokster, eDonkey2000, BearShare, Morpheus, and KaZaA file-sharing networks. This worm may distribute itself across the mapped drives and through AIM95, mIRC, and ICQ.

W32.HLLW.Backzat.G deletes the security software from your computer.

The email it sends has the following characteristics:

Subject: Fw: Hello there.
Message: Hey, I just recieved a screen saver in the mail and it is really cute. Take a loot.
Attachment: CuteKirby.Scr

This threat is written in the Microsoft C++ programming language and is compressed with UPX.

Protection

• Virus Definitions (LiveUpdate™ Weekly) January 22, 2003
• Virus Definitions (Intelligent Updater) January 22, 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: Medium
• Large Scale E-mailing: Sends itself to all the contacts in the Microsoft Outlook Address Book.
• Deletes Files: Attempts to delete the files from various security software products.
• Modifies Files: Overwrites all the .doc and .txt files in C:, C:\%Windir%, C:\%Windir%System, and C:\%Windir%System32. Overwrites the .exe files in C:\%Windir%.

Distribution

• Distribution Level: Low
• Subject of Email: Fw: Hello there.
• Name of Attachment: CuteKirby.Scr
• Size of Attachment: 108,544 bytes
• Target of Infection: Attempts to spread through the Grokster, eDonkey2000, BearShare, Morpheus, KaZaA, AIM95, mIRC, ICQ, and mapped drives

TECHNICAL DETAILS

When W32.HLLW.Backzat.G runs, it does the following:

1. Displays this fake message:
   
   
   
2. Copies itself as:
   • C:\%System%CuteKirby.Scr
   • C:\%System%TaskSystemDll.Exe
     
     NOTES: %System% is a variable. The worm locates the Windows system folder and copies itself to that location. By default, this is C:WindowsSystem (Windows 95/98/ME), C:WindowsSystem32 (Windows XP), or C:WinntSystem32 (Windows 2000/NT).
     
     
3. Copies itself as Kirbster.exe to all the drives from D to Z.
   
4. Adds the value:
   
   WinSysStartUpWKbLw C:\%System%TaskSystemDll.Exe
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   
   so that the worm runs when you start Windows.
   
5. Creates C:\%Windir%Kirbybmp.bmp, which is not a malicious bitmap file. It is 1,782 bytes in length.
   
   NOTE: %Windir% is a variable. The worm locates the Windows installation folder and copies itself to that location. By default, this is C:Windows or C:Winnt.
   
6. Modifies the value of Wallpaper to:
   
   Wallpaper C:\%windir%Kirbybmp.bmp
   
   in the registry key:
   
   HKEY_CURRENT_USERControl PanelDesktop
   
7. Adds the value:
   
   SCRNSAVE.EXE C:\%system%CuteKirby.Scr
   
   in the registry key:
   
   HKEY_CURRENT_USERControl PanelDesktop
   
8. Creates C:\%Windir%KirbyWins.mp3, which is not a malicious Winamp media file. It is 66,003 bytes in length. Then, the worm opens this mp3 file.
   
9. Locates the KaZaA transfer folder by retrieving the value from the registry key:
   
   HKEY_CURRENT_USERSoftwareKazaaTransferDlDir0
   
   If the KaZaA transfer folder exists, the worm copies itself as:
   • C:Program FilesGroksterMy GroksterAFI - 6 to 8.Mp3.Exe
   • C:Program FilesEDonkey2000IncomingFeeder - Under The Weather.Mp3.Exe
   • C:Program FilesBearShareSharedTherion - Nifelheim.Mp3.Exe
   • C:Program FilesMorpheusMy Shared FolderPennyWise - Land Of The Free.Mp3.Exe
   • C:Program FilesICQShared FilesWinIso - Iso Ripper.Exe
   • C:My DownloadsePs2e - PS2 Emulator.Exe
   • <The KaZaA transfer folder>Rage Against The Machine - Sleep Now In This Fire.Mp3.Exe
     
     NOTE: The Grokster, eDonkey2000, BearShare, KaZaA, Morpheus, or ICQ software must be installed on the computer for the worm to spread in those networks.
     
     
10. Locates the mIRC folder by retrieving the value from the registry key:
    
    HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionUninstallmIrc
    
11. If mIRC is installed, the worm creates the file Script.ini in the mIRC folder, which the worm uses to send copies of itself to other mIRC users.
    
12. Copies itself as C:Program FilesAIM95CutiePinkKirby.Scr and enables the AIM95 users to share this file.
    
13. Attempts to overwrite all the .exe files with itself. Due to the bugs in the worm code, the worm overwrites only one .exe file in the C:\%Windir% folder each time it runs.
    
14. Performs the following, if the system day is Sunday:
    1. Creates the following files:
       • KirbyFlooder.Vbs, which is 88 bytes in length
       • KirbyFlooder.Bat, which is 110 bytes in length
       • C:Kirbymail.vbs
    2. Uses C:Kirbymail.vbs to send itself to all the contacts in the Microsoft Outlook Address Book. The email has the following characteristics:
       
       Subject: Fw: Hello there.
       Message: Hey, I just recieved a screen saver in the mail and it is really cute. Take a loot.
       Attachment: CuteKirby.Scr
       
    3. Deletes all the files in these folders:
       • C:PC-Cil~1
       • C:ToolKitFindVirus
       • C:AntiVi~1
       • C:VS95
       • C:TBAVW95
       • C:f-macro
       • C:eSafen
       • C:Progra~1FindVirus
       • C:Progra~1FWIN32
       • C:Progra~1QuickH~1
       • C:Progra~1AntiVi~1
       • C:Progra~1GrisoftAVG6
       • C:Progra~1AvPersonal
       • C:Progra~1Trojan~1
       • C:Progra~1Kasper~1
       • C:Progra~1TinyPe~1
       • C:Progra~1oneLa~1oneAlarm
       • C:Progra~1Comman~1F-PROT95
       • C:Progra~1TrendM~1Pc-cil~1
       • C:Progra~1PandaS~1PandaA~1
       • C:Progra~1eSafeProtect
       • C:Progra~1McAfeeMcAfee FireWall
       • C:Progra~1McAfeeVirusScan
       • C:Progra~1Common~1Symant~1Script~1
       • C:Progra~1Common~1Symant~1
       • C:Progra~1Symantec
       • C:Progra~1Norton~2
       • C:Progra~1Norton~1
    4. Overwrites all the .doc and .txt files with the text "L0NEw0lf was here..." in the following folders:
       • C:
       • C:\%Windir%
       • C:\%Windir%System
       • C:\%Windir%System32

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

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_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   In the right pane, delete this value:
   
   WinSysStartUpWKbLw C:\%system%TaskSystemDll.Exe
   
4. Navigate to the registry key:
   
   HKEY_CURRENT_USERControl PanelDesktop
   
   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.