Infostealer.Tarno.B

1. Creates the following files:
   • %Windir%\Svchost.exe: The main component of the Trojan, which performs reporting and logging.
   • %System%\Wingua.exe: Drops the file, mstu.exe.
   • %Windir%\Sysini.ini: This file is not malicious, and therefore, Symantec antivirus products do not detect it. However, it may contain user names and passwords, which the Trojan captured, and thus should be deleted. It can be easily recognized by the string:
     
     ***Computer was successfully infected***
     
     which occurs at the beginning of the file.
     
     
   • %Windir%\Mstu.exe: This creates a service "anem," which monitors process lists, which looks for the processes. For a list of the processes it looks for, refer to the Additional Information section at the end of this document.
     
     It terminates any processes it finds.
     
     
   • %Windir%\Msto32.dll: This file contains functions to log keystrokes.
     
     

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     Notes:
     -- %Windir% is a variable. The Trojan locates the Windows folder and drops the files in that location. By default, this is C:\Windows\ (Windows 95/98/Me/XP) or C:\Winnt\ (Windows NT/2000).
     -- %System% is a variable. The Trojan locates the System folder and drops the files 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. Adds the value:
   
   "Online Service"="%Windir%\svchost.exe"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
   
   so that the Trojan is executed on startup.
   
   
3. If the Trojan is running on a Windows 95 or Windows 98 system, it uses the RegisterServiceProcess API to register itself as a service process. This means that it will continue running after you have logged out and it will not be visible in the list of processes.
   
   
4. Deletes all the entries in the URL cache.
   
   
5. Installs hook procedures into a hook chain to monitor the system for any keyboard messages. The keyboard hook procedures process the messages and pass the hook information to the next hook procedure in the current hook chain. This permits Infostealer.Tarno.B to intercept key strokes.
   
   
6. Captures typed keystrokes and stores them, together with the IP address of the computer and the current user's login name in the file, %Windirs%\Sysini.ini.
   
   
7. Sends the Sysini.ini file to a predetermined email address, via a predetermined SMTP server, 194.67.23.10.
   
   
8. Runs the remote php script www.moncash.net/command.php and can perform a number of different actions based on its response, such as:
   • Upload a file to a specific server
   • Kill a specific process
   • Search for the existence of a specified file
   • Delete a specified file
   • Update itself
   • Execute a specified command

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.