Troj.Polyglot

When Y2Kcount.exe is executed or launched, it extracts its contents:

• Project1.exe
• File002.dat
• File003.dat
• File004.dat
• File001.dat

Next, it executes the Project1.exe to install itself. Once it finishes its installation, it displays a fake error message: "Password protection error or invalid CRC32!"

This Trojan horse makes the following modifications to the computer:

1. It drops several files into the \Windows\System folder:
   • Proclib.exe
   • Proclib.dll
   • Proclib16.dll
   • Ntsvsrv.dll
2. It appends Ntsvsrv.dll into the drivers= line in the [boot] section of the System.ini file. This modification loads the Trojan every time the system restarts.
3. It modifies the registry entry ...\Shell\OpenHomePage\Command to @="C:\WINDOWS\SYSTEM\PROCLIB.EXE". This modification loads Proclib.exe upon Web/Internet access.
4. Upon the next system reboot, it will also rename the Wsock32.dll file to Nlhvld.dll and replace it with Proclib16.dll. This allows the Trojan to hook network (specifically Internet) connection activity.

This Trojan hooks four WSOCK32 API functions: connect, recv, send, and closesocket. It appears to search for user names, passwords and login ids. It is able to scan incoming and outgoing data through the Internet. The Trojan creates a temporary data file on the hard disk to store its information. The name of the file is MySharedFileNameForMyDLL. It also launches another process that reads this temporary data file. That process contains code to connect to mail.compuserve.com and send an email message to BTKBoss@usa.net. This process runs as a service. So it does not appear in the task list and remains running if the user logs off the system and logs on again.

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