W32.HLLW.Yoof

When it is run, W32.HLLW.Yoof does the following:

It copies itself as %system%\SystemConfig.exe.

NOTE: %system% is a variable. The worm locates the System folder and copies itself to that location. By default this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).

The worm adds the value

Windows System Configure    %System%\SystemConfig.exe

to these registry keys:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\
CurrentVersion\RunServices

so that it runs each time that you start Windows.

Some variants also download a file named C:\Uninstall.exe. If the worm downloads and executes this file, it then downloads a file named C:\Unwise.exe and sends an ICQ page to the virus creator.

The worm then creates the%system%\Media folder. It then configures this folder to be a shared KaZaA folder by making the following registry modifications:

• It adds the values
  
  Dir0 %system%\Media
  Dir1 %system%\Media
  Dir2 012345:%System%\Media
  Disable Sharing 0
  
  to the registry key
  
  HKEY_CURRENT_USER\Software\Kazaa\LocalContent
  
• It adds the values
  
  DlDir0 012345:%system%\Media
  DlDir1 %system%\Media
  DlDir99 012345:%system%\Media
  
  to the registry key
  
  HKEY_CURRENT_USER\Software\Kazaa\Transfer
  
• It adds the value
  
  Sharedir %System%\Media
  
  to the registry key:
  
  HKEY_LOCAL_MACHINE\Software\Kazaa\Cloudload

Finally, it copies itself to %system%\Media as the following files:

• Jenna Jamison Dildo Humping.exe
• Pamela Anderson And Tommy Lee Home Video.exe
• Alicia Silverstone Payboy Nude.exe
• Kama Sutra Tetris.exe
• Flash Golf.exe
• Hoes For You Solitare.exe
• Bingo.exe
• Irc Client.exe
• Mirc 7.0.exe
• Email Bomber.exe
• FileServer.exe
• Kazaa Clone.exe
• Napster Clone.exe
• Winmx.exe
• Website Hacker.exe
• Hotmail Hacker.exe
• Windows Hacker.exe
• Free Porn.exe
• Free Mpegs.exe
• Free Pics.exe
• Xbox Emulator.exe
• Britney Spears Dance Beat.exe
• Shakira Dancing.exe
• J.Lo Bikini Screensaver.exe
• Universal Game Crack.exe
• Soldier Of Fortune 2 Mutiplayer Serial Hack.exe
• Play Games Online For FREE.exe
• Win A Ps2.exe
• Win An Xbox.exe
• Ps2 Emulator.exe
• Ps2 Iso 2 Rom Converter.exe
• Xbox Iso 2 Rom Converter.exe
• The Sims Game Crack.exe
• Working Iso Burner.exe
• Winzip.exe
• Winrar.exe
• Winace.exe
• System Monitor.exe
• Warcraft 3 Battle.net Crack.exe
• DDos Client.exe

Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

• Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
• 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.
• Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
• Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
• Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
• Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
• If a 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.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate compromised computers quickly to prevent threats from spreading further. 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.
• If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
• For further information on the terms used in this document, please refer to the Security Response glossary.

Summary