Trojan.Jasbom

When the malicious URL is clicked, the default browser goes to a Web page on the j4sb.com domain. The HTML Web page attempts to exploit the Microsoft Internet Explorer ITS Protocol Zone Bypass Vulnerability (as described in the Microsoft Security Bulletin MS04-013) to execute a .CHM file on the same site.

The code contained in the .CHM file executes #.exe, also contained inside the CHM file.

When #.exe is executed, it performs the following actions:

1. Drops the following files:
   
   
   • %System%\explorer.exe
   • %System%\htdll.dll
   • C:\GaMeJTT1.TXT
     
     Note: %System% is a variable that refers to the System folder. By default this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).
     
     
2. Terminates the ZoneAlarm and Romanian Antivirus applications, as well as the following processes:
   
   
   • EGHOST.EXE
   • MAILMON.EXE
   • KAVPFW.EXE
   • Iparmor.exe
   • Ravmon.exe
     
     
3. Closes windows that have any of the following 3 strings of Chinese characters in the title:
   
   
   
   Note: These windows are associated with a Chinese Antivirus product.
   
   
4. Adds the value:
   
   "load" = "%System%\explorer.exe"
   
   to the registry subkey:
   
   HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows
   
   so that the Trojan is executed every time Windows starts.
   
   
5. Uses htdll.dll to log keystrokes and mouse clicks sent to the application Lineage to C:\GaMeJTT1.TXT.
   
   
6. Uses htdll.dll to dump certain regions in memory of the application Lineage to C:\GaMeJTT1.TXT.
   
   
7. Sends system information and logged keystrokes to a script on the j4sb.com domain on port 80.
   
   
8. On computers running Windows 9x/ME, the Trojan backs up %Windir%\rundll32.exe and %System%\internat.exe to the following locations:
   
   
   • %SystemDrive%\rundll32.exe
   • %SystemDrive%\internat.exe
     
     Note: %SystemDrive% is a variable that refers to the drive on which Windows is installed. By default, this is drive C.
     
     
9. On computers running Windows 9x/ME, the Trojan copies itself to:
   
   
   • %Windir%\rundll32.exe
   • %System%\internat.exe
     
     
10. If the Trojan fails to copy itself to these locations, it will create a temporary copy of itself as:
    
    
    • %Windir%\rundll32.exe.ddd
    • %System%\internat.exe.ddd
      
      
11. On computers running Windows 9x/ME, the Trojan adds the following text to the [rename] section of WININIT.INI:
    
    [rename]
    %Windir%\rundll32.exe=%Window%\Rundll~1.ddd
    %System%\internat.exe=%Window%\intern~1.ddd

 

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