Backdoor.IRC.Ratsou

Backdoor.IRC.Ratsou may be downloaded by Trojan.Downloader.Aphe from the Web site, http:/ /amateur.freegayspace.com.

When Trojan.Downloader.Aphe runs, it may download a file as C:\Roof.exe, which is also detected as Trojan.Downloader.Aphe, from a specific Web site. Then, the Trojan executes C:\Roof.exe.

C:\Roof.exe downloads a third file as C:\Newconf.exe, which is detected as Backdoor.IRC.Ratsou, from the same Web site. Then, the Trojan executes C:\Newconf.exe.

When C:\Newconf.exe runs, it does the following:

1. Creates the folder, %Windir%\Help\Tours.
   
   NOTE: %Windir% is a variable. The Trojan locates the Windows installation folder (by default, this is C:\Windows or C:\Winnt) and copies itself to that location.
   
   
2. Creates the following files in the Windows installation folder:
   • AIM.TXT, which is a text file.
   • AIMIRC.INI, which is a text file.
   • BNC.DLL (5,573 bytes), which is a script file.
   • DTKODE.TXT (101,914 bytes), which is a script file.
   • REMOTE.INI, which is a script file.
   • SCRIPT1.DLL (610 bytes), which is a script file.
   • SPIG.TXT (4,340 bytes), which is a script file.
   • SYSBOOT.DLL (453 bytes), which is a script file.
   • TEMP (24,515 bytes), which is a script file.
   • UNICOD_R (877 bytes), which is a script file.
   • WIND.DLL (3,849 bytes), which is a script file.
   • IPSERVER.TXT, which is a text file that contains some URLs.
   • NICKS.TXT, which is a text file that contains mIRC nicknames.
   • UNICOD_L, which is zero bytes when created.
   • BOOT.exe (35,328 bytes), which is a legitimate remote process launcher, Psexesvc.exe. The Trojan attempts to use this utility to copy itself to other systems.
   • EMPAVMS.exe (20,992 bytes), which is a legitimate utility used to hide windows.
   • LIBPARSE.exe (25,600 bytes), which is a process viewer.
   • MOO.DLL (34,304 bytes).
   • NHTML.DLL (6,656 bytes).
   • RESTART.exe (37,888 bytes), which is a utility used to reboot the computer.
   • BLA.TXT (8,397 bytes), which is Backdoor.IRC.Flood.
   • CRAZY.exe (17,408 bytes), which is Hacktool.DoS.
   • CONFIG.HFG (6,209 bytes), which is IRC Trojan.
   • CSCAN.DAT (2,017 bytes), which is IRC Trojan.
   • IMPVMS.DLL (18,355 bytes), which is IRC Trojan.
   • MSCCL.DLL (18,919 bytes), which is IRC Trojan.
   • NVDRV.OCX (18,920 bytes), which is IRC Trojan.
   • REG.XPL (2,707 bytes), which is IRC Trojan.
   • SYSTE32.DLL (1,603 bytes), which is IRC Trojan.
   • MICONFIG.exe (14,336 bytes), which is Hacktool.
   • System.exe (17,920 bytes), which is Hacktool.
   • lan.bat (84,694 bytes), which is BAT.Trojan.
   • Wincmd34.bat (30,993 bytes), which is BAT.Trojan.
   • Expl32.exe (629,760 bytes), which is Backdoor.IRC.Ratsou. This file is a patched version of mIRC.exe.
   • Ratsou.exe (2,351 bytes), which is Trojan.Downloader.Aphe.
     
     
3. Adds the value:
   
   "explorer"="%Windir%\help\tours\expl32.exe"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
   
   so that this patched mIRC program runs when you restart Windows.
   
   
4. Hooks the IRC file extensions in HKEY_LOCAL_MACHIN\Software\Classes that call %Windir%\help\tours\expl32.exe when chat files are opened.
   
   
5. Runs %Windir%\help\tours\expl32.exe in the background.
   
   
6. Uses the dropped impvms.dll file to connect to some randomly generated IP addresses. Then, the Trojan uses the dropped batch files to connect to the remote IPC$ and ADMIN$ shares on each of the IP addresses that it finds, by using various user name and password pairs, and attempts to copy and run the Ratsou.exe file on the remote systems.

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