Backdoor.Lithium

The Backdoor.Lithium consists of several components:

• The server component, which resides on a host computer.
• The client component, which the hacker uses to manipulate the host computer.
• The installer, which drops the Trojan components.
• The .dll file, which is a screen capture program that the server program uses.

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Notes:

• The exact file names may vary from version to version because the hacker who creates the Trojan can choose any file names. For example, the installer can be named C:\%System%\Registry32.exe.
• Backdoor.Lithium may arrive as a component of the W32.Blaster.C worm. However, Backdoor.Lithium will not spread W32.Blaster.C itself. You should not see any instances of the Backdoor on clients, other than on the original infected host.

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When the Backdoor.Lithium runs, it performs the following actions:

1. Drops the server component into the %Windir% and %System% folders. Some names that have been reported include Iexplorer.exe, Bnkl32.exe, Ls.exe, Root32.exe, Shell.exe, and Shell32.com.
   
   

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

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2. Drops the .dll file in the %System% folder. This file may be named Sv_cap.dll, Pw.dll, C32.dll, Tdcp32.dll, or Tdpw32.dll.
   
   

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   Note: The .dll component is a screen capture program. It is not viral by itself, and therefore Norton AntiVirus does not detect it.

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3. Adds one or more of the values:
   
   • "Registry Services" = "C:\WINDOWS\SYSTEM\Registry32.exe"
   • "Shell32" = "Iexplorer.exe"
   • "Iexplore Services"="iexplore.exe"
   • "Windows Root Account" = "Root32.exe"
     
     to the registry key:
     
     HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
     
     
4. May add one or more of the values:
   
   • "Windows Root Account" = "Root32.exe"
   • "Shell32" = "Shell32.com"
     
     to the registry key:
     
     HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\
     RunServices
     
     
5. Opens TCP/UDP port(s) on a compromised computer, giving a remote attacker unobstructed access to your computer. The port(s) may vary, but by default, the port number is 31416; though, there have been reported cases of port 37 being used.
   
   
6. Some variants will post a notification containing the server information to www.t33kid.com, such as IP address, port, operating system, and so on.

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