Backdoor.IRC.Cloner

Backdoor.IRC.Cloner typically arrives as a large executable file. The file is usually sent by email, but is sometimes sent through IRC.

When Backdoor.IRC.Cloner is executed, it typically performs the following actions:

1. Creates a new subfolder in the %System% folder; although, some variants use %Windir%\System32. A typical name of this folder is %System%\Spool\Drivers\E3.
   
   NOTES:
   • %Windir% is a variable. The Trojan locates the Windows installation folder (by default, this is C:\Windows or C:\Winnt) and creates the folder in that location.
   • %System% is a variable. The Trojan locates the System folder and creates the folder in 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).
     
2. Inserts several files into the folder that the Trojan the created. Some examples of the file names are:
   • Abc.bat
   • Abc.dll
   • Abc.exe
   • Abcd.jpg
   • Attrib.exe *
   • Dtceindll32.dll
   • Hot.dll
   • Identd.exe *
   • Kill.exe *
   • Lsass.exe *
   • Moo.dll *
   • Psexec.exe *
   • Reg3.ocx
   • Regsvc.exe *
   • Remote.ini
   • Run32.bat
   • Set.bat
   • Shell32.bat
   • Shell32.dll
     
     NOTE: The files marked with an asterisk (*) are legitimate Windows or commercial files that Backdoor.IRC.Cloner has exploited. These files are not malicious, and as such, Symantec antivirus products do not detect them.
     
3. Creates one registry value so that the Trojan is executed each time you start Windows. This value is typically located in either of these keys:
   
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\
   CurrentVersion\RunServices
   
   The value added to the key will refer to one of the files within one of the folders (added by the Trojan). For example, one variant creates the value:
   
   MSKCES32 %windir%\System32\SPOOL\DRIVERS\E3\shell32.bat
   
   in the key:
   
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\
   CurrentVersion\RunServices
   
4. Logs into an IRC channel, through which the attacker can control the Trojan.

Other functionalities of Backdoor.IRC.Cloner include:

• Uploading and downloading files to and from your computer
• Executing programs and scripts on your computer
• Flooding the IRC channels
• Flooding mailboxes (mailbombing)
• Opening a listening port on your computer, such as port 65,004
• Connecting through port 6,667 to IRC
• Initiating a copy functionality, whereby Backdoor.IRC.Cloner will try to copy itself to and execute on another computer on your network, if that particular computer has an open share that is protected with an easily guessed password.

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