W32.HLLW.Anig

• %System%\NTOSA32.exe
• %System%\NTGINA.dll, which logs user keystrokes
• %System%\NTKBH32.dll, which contains keystrokes and passwords. As this file is not malicious, Symantec products do not detect it.
  
  

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  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).

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1. Adds the value:
   
   "Osa32" = "NTOSA32.exe"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
   
   so that the worm runs when you start Windows.
   
   
2. Creates the registry key:
   
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\dfcsvc
   
   with the values:
   
   • "DependOnGroup"=""
   • "DependOnService"="RpcSS"
   • "DisplayName"="Distributed File Controller"
   • "Error Control"="0x0"
   • "ImagePath"="NTOSA32.exe /dfcsvc"
   • "ObjectName"="LocalSystem"
   • "Start"="0x2"
   • "Type"="0x110"
     
     which registers a service named Distributed File Controller.
     
     
3. Creates two temporary files named <random characters>.vda in the same folder from which the worm is executed. These files will either be two copies of a .dll file named Ntgina.dll or a copy of the worm itself and a copy of Ntgina.dll.
   
   
4. Adds the value:
   
   "GinaDll"="ntgina.dll"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
   
   which allows the worm to capture all the successful login user names and passwords.
   
   
5. Adds the values:
   
   • "Ram32Data"="<random alphabetical characters>"
   • "Ram32ID"="<random alphabetical characters>"
   • "Ram32Group"="<random alphabetical characters>"
     
     to the registry key:
     
     HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
     
     
6. Enumerates the network resources and attempts to log in to the admin share on the remote machine using the current user's credentials. If successful, the worm will perform the following actions:
   
   1. Copies %System%\NTOSA32.exe to \\<remote machine>\ADMIN$\SYSTEM32\NTOSA32.exe. If the worm is unsuccessful, it assumes the remote machine is already infected and will skip all of the following steps.
      
      
   2. Adds the value:
      
      "Osa32" = "NTOSA32.exe"
      
      to the registry key:
      
      HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
      
      on the remote machine.
      
      
   3. Copies %System%\NTGina.dll to \\<remote machine>\ADMIN$\SYSTEM32\NTGina.dll. If the worm is unsuccessful in copying itself to this location, it will not add the following associated registry key.
      
      
   4. Adds the value:
      
      "GinaDll"="ntgina.dll"
      
      to the registry key:
      
      HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
      
      on the remote machine.
      
      
   5. Adds the value:
      
      "Ram32Group"="<random alphabetical characters>"
      
      to the registry key:
      
      HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
      
      
   6. Registers and starts NTOSA32.exe as a remote service on the remote machine allowing remote execution of the threat. Registering NTOSA32.exe as a service creates the following registry key:
      
      HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\dfcsvc
      
      with the values:
      
      • "DependOnGroup"=""
      • "DependOnService"="RpcSS"
      • "DisplayName"="Distributed File Controller"
      • "Error Control"="0x0"
      • "ImagePath"="NTOSA32.exe /dfcsvc"
      • "ObjectName"="LocalSystem"
      • "Start"="0x2"
      • "Type"="0x110"
        
        
7. Stores keystrokes, passwords, and an infection log in the file, %System%\NTKBH32.dll.
   
   
8. Opens a backdoor on TCP port 5190 and listens for commands from the attacker. When the attacker connects and sends a specific command, the worm may reconnect to the attacker, with a destination port of 5190. This traffic may appear to be ICQ messaging traffic.
   
   
9. Connects to a predetermined IP address, with destination port 5190, sends system information, and waits for commands. This traffic may also appear to be ICQ messaging traffic.

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.