Backdoor.Netbus.444051

Netbus Pro version 2,1 is a remote-control tool. Netbus Pro version 2,1 has been redesigned such that it no longer runs stealth by default. After installing it, one must specifically allow it to run stealth. However, Backdoor.Netbus.444051 comes as a package containing a Windows registry file, a picture, and the Netbus executable.

When executed, this package does the following:

1. Creates and runs the registry file Extrac16.reg from the \Windows folder. This file contains settings for Netbus so that it will run stealth.
2. Inserts the Netbus Pro executable file in the Temp folder, normally \Windows\Temp. The name of the file can change, but it will always start with Pkg and end with .exe. For example, the name could be PKGd7g8.exe or Pkg22c4.exe.
3. Creates a "Netbus Server Pro" value in the Windows registry at:
   
   HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServices
   
   This ensures execution on reboot.
4. Executes the Netbus Pro executable. Due to the fact that the information from the registry file has been applied prior to Netbus being executed, no activity appears on the screen.

To further hide its malicious actions, this backdoor Trojan attempts to trick you into believing it is a picture. When the file has been executed, after performing all the malicious actions, this backdoor Trojan will display a picture.

By default, this variant of Netbus will open port 20034.

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