W32.Remabl.Worm

W32.Remable.Worm consists of one .dll file and two .exe files. The file names are usually the following:

• Shambl3r.exe: Self-extracting zip file contains many python scripts.
• Sys.exe: Symantec Security Response has not received this file yet.
• Python23.dll: legitimate dll file for Python scripts.

When W32.Remable.Worm is executed, it does the following:

1. Obtains network information by using the ipconfig command and then upload the information to a predetermined FTP site.
   
   
2. Creates %Windows%\Cnf.bat, which will run Sys.exe. This may allow the author of the program to access command.com or cmd.exe on the infected computer from a remote computer by using a predetermined username and password.
   

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   Note: %Windir% is a variable. The worm locates the Windows installation folder (by default, this is C:\Windows or C:\Winnt) and copies itself to that location.

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3. Add the following lines to the [windows] section of the Win.ini file on Windows 95/98/Me computers:
   
   run=%Windows%\cnf.bat
   load=%Widnows%\shambl3r.exe
   
   
4. Adds the values:
   • "shambl3r"="C:\%Windows%\cnf.bat"
   • "shambl3r2"="C:\%Windows%\shambl3r.exe"
   • "shambl3r3"="C:\%Windows%\shambl3r.exe"
   • "shambl3r4"="C:\%Windows%\shambl3r.exe"
   • "shambl3r5"="C:\%Windows%\shambl3r.exe"
   • "shambl3r6"="C:\%Windows%\shambl3r.exe"
   • "shambl3r7"="C:\%Windows%\shambl3r.exe"
   • "shambl3r8"="C:\%Windows%\shambl3r.exe"
   • "shambl3r9"="C:\%Windows%\shambl3r.exe"
   • "shambl3r10"="C:\%Windows%\shambl3r.exe"
   • "shambl3r11"="C:\%Windows%\shambl3r.exe"
     
     to the registry key
     
     HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
     
     on Windows NT/2000/XP computers.
     
     
5. Creates a random IP addresses each time the worm is executed.
   
   
6. Pings the IP addresses and if a response is received, tries to connect following folders:
   • X:\Documents and Settings\All Users\Men・Inicio\Programas\Inicio
   • X:\Documents and Settings\All Users\Start Menu\Programs\Startup
   • X:\Dokumente und Einstellungen\All Users\Start Menu\Programs\Startup
   • X:\Documenti e Impostazioni\All Users\Start Menu\Programs\Startup
   • X:\WINNT\Profiles\All Users\Start Menu\Programs\Startup
   • X:\WINNT\Profiles\All Users\Men・Inicio\Programas\Inicio
   • X:\WINDOWS\Start Menu\Programs\Startup
   • X:\WINDOWS\Men・Inicio\Programas\inicio
   • X:\WINDOWS\All Users\Start Menu\Programs\Startup
   • X:\WINDOWS\All Users\Men・Inicio\Programas\Inicio
   • X:\Documents and Settings\All Users\Menu Inicio\Programas\Inicio
   • X:\Documents and Settings\All Users\Menu Inicio\Programas\startup
   • X:\Documents and Settings\All Users\Menu Iniciar\Programas\Inicializar
   • X:\Dokumente und einstellungen\all users\Startmen・programme\autostart
   • X:\Documents and settings\All users\Menu avvio\Programmi\Esecuzione automatica
   • X:\Documents and Settings\All Users\Menu Iniciar\Programas\startup
   • X:\Documents and Settings\All Users\Menu Iniciar\Programas\Inicio
   • X:\WINDOWS\All Users\Startmenue\Programme\Autostart
   • X:\WINDOWS\Startmenue\Programme\Autostart
   • X:\Windows\Menu Iniciar\programas\Iniciar
   • X:\Windows\Menu D駑arrer\Programmes\D駑arrage
   • X:\Windows\Startmen・Programme\Autostart
   • X:\Windows\menu avvio\programmi\esecuzione automatica
   • X:\Documents and settings\All users\Start-meny\Program\Autostart
   • %s\Start Menu\Programs\Startup
   • %s\Men・Inicio\Programas\inicio
   • %s\All Users\Start Menu\Programs\Startup
   • %s\All Users\Men・Inicio\Programas\Inicio
   • %s\Profiles\All Users\Start Menu\Programs\Startup
   • %s\Profiles\All Users\Men・Inicio\Programas\Inicio
     
     
7. Copies Shaml3r.exe, Sys.exe and Python23.dll to the folders above.
   
   
8. Attempts to connect to other computers within the same network range as the randomly generated IP address.
   
   For example, if the randomly generated IP address is A.B.C.D, the worm will then attempt to connect to all computers with an IP address that begins with A.B.x.x.

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