Backdoor.IRC.RPCBot

Backdoor.IRC.RPCBot is a collection of batch files, script files, utilities, as well as hacktools. It is possible that the names and functions of the files may change. The information discussed in this writeup is based on the samples that Security Response has reviewed.

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Note: In the list of following files, the file sizes are in bytes (contained in parentheses).

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The files associated with Backdoor.IRC.RPCBot are:

• Click.exe (32,768), which is a Hacktool
• SFind.exe (266,752), which is a Hacktool
• Wmpx.exe (43,383), which is a Hacktool.DoS
• WinOLE.exe (572,928) , which is a Trojan Horse

The following components are detected as Backdoor.IRC.RPCBot:

• Deploy.bat (274)
• Unrar.bat (169)
• Wx11.bat (109)
• Wx12.bat (194)
• Start.dll (6,153), which is an IRC script file
• Jesus.dll (4,254), which is an IRC script file
• LucomServer.dll (802), which is an IRC script file
• Msoft.dll (206), which is an IRC script file
• Users.dll (75,017), which contains many IRC nicknames
• Reg.reg (773)
• Service.txt (176)
• Wx12.exe (19,618), which the Trojan uses to exploit the DCOM RPC vulnerability
• Bot.rar, which is a rar file that contains all the components of the Trojan

The following components are clean utilities that the Trojan uses. Therefore, Symantec antivirus products do not detect them. If the threat infected your computer, you can manually delete them if desired:

• Bnc.cfg (76)
• Cygwin1.dll (971,080)
• Drvx.dll (2,853)
• Clear.exe (28,672)
• CRC.exe (24,096)
• Dhcpp.exe (69,632)
• Events.exe (134,656)
• Nctl.exe (569,344)
• Pslist.exe (49,152)
• Q019204.exe (21,584)
• Service.exe (63,488)
• UnRAR.exe (194,048)

When Backdoor.IRC.RPCBot runs, it does the following:

1. Creates the folder, C:\RECYCLER\S-1-5-21-57989841-1715567821-725345543-1004\LOGS, and copies Bot.rar into this folder.
   
   
2. Runs WinOLE.exe as a service. WinOLE.exe is a patched mIRC client program, and hooks the IRC file extensions in HKEY_LOCAL_MACHIN\Software\Classes, which call WinOLE.exe when chat files are opened.
   
   
3. Runs the file, Dhcpp.exe, which is a TFTP server.
   
   
4. Runs the file, Nctl.exe, which is an FTP server.
   
   
5. Runs the file, Events.exe, which is an IRC proxying server.
   
   
6. Sets the following values:
   
   "BaseDirectory"="C:\RECYCLER\S-1-5-21-57989841-1715567821-725345543-1004\LOGS"
   "TftpPort"="00000045"
   "Hide"="00000001"
   "WinSize"="00000000"
   "Negociate"="00000000"
   "DirText"="00000000"
   "ShowProgressBar"="00000000"
   "Timeout"="00000003"
   "MaxRetransmit"="00000006"
   "SecurityLevel"="00000000"
   "UnixStrings"="00000000"
   "LocalIP"=""
   "Beep"="00000000"
   "VirtualRoot"="00000000"
   "Services"="00000003"
   "TftpLogFile"=""
   "SaveSyslogFile"=""
   
   in the registry key:
   
   HKEY_LOCAL_MACHINE\SOFTWARE\TFTPD32
   
   
7. Sets the value:
   
   "DisableWebDAV"="00000001"
   
   in the registry key:
   
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W3SVC\Parameters
   
   
8. Sets the values:
   
   "EnableDCOM"="N"
   "EnableRemoteConnect"="N"
   
   in the registry key:
   
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Ole
   
   
9. Connects to specified IRC servers and joins a channel to listen for commands from the Trojan's creator.
   
   One such command is to exploit the DCOM RPC vulnerability: The Trojan connects to some randomly generated IP addresses to find computers that are listening at TCP port 135. Once the computer is found, it sends specially formed data, which exploits the DCOM RPC vulnerability, to that computer.
   
   If the Trojan is successful, it may create a folder:
   
   C:\RECYCLER\S-1-5-21-57989841-1715567821-725345543-1004\LOGS
   
   and TFTP its components, bot.rar, unrar.bat, and unrar.exe, to the computer, and then runs itself there.

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