Backdoor.Win32.TERRALOADER.A

This Backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites. It may be downloaded by other malware/grayware/spyware from remote sites.

It executes commands from a remote malicious user, effectively compromising the affected system. It connects to a website to send and receive information.

It deletes itself after execution.

Arrival Details

This Backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It may be downloaded by other malware/grayware/spyware from remote sites.

Installation

This Backdoor drops the following files:

• %ProgramData%\Microsoft\{random characters}.txt <- JavaScript used to execute the other .txt dropped file
• %ProgramData%\Microsoft\{random characters}.txt <- contains malicious XSL backdoor script

(Note: %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This contains application data for all users. This is usually C:\ProgramData on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit), or C:\Documents and Settings\All Users on Windows Server 2003(32-bit), 2000(32-bit), XP.)

It drops the following non-malicious file:

• %ProgramData%\Microsoft\msxsl.exe

(Note: %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This contains application data for all users. This is usually C:\ProgramData on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit), or C:\Documents and Settings\All Users on Windows Server 2003(32-bit), 2000(32-bit), XP.)

It adds the following processes:

• %ProgramData%\Microsoft\msxsl.exe {filename of XSL backdoor script}.txt {filename of XSL backdoor script}.txt

(Note: %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This contains application data for all users. This is usually C:\ProgramData on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit), or C:\Documents and Settings\All Users on Windows Server 2003(32-bit), 2000(32-bit), XP.)

Other System Modifications

This Backdoor adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Notepad
{Computer name} = {scheduled task name},{filename of XSL backdoor script},{filename of JavaScript file}

Backdoor Routine

This Backdoor executes the following commands from a remote malicious user:

• d&exec - download and execute PE file
• more_eggs - update itself
• gtfo - uninstall itself
• more_onion - execute additional script
• more_power - execute arbitrary commands

It connects to the following websites to send and receive information:

• https://drive.{BLOCKED}content.kz/drive/info

Information Theft

This Backdoor gathers the following data:

• Computer Serial Number
• Hardware Information
• Volume Label and Volume Serial Number of %HOMEDRIVE%
• List of AV Products Installed
• User Name
• Computer Name
• OS Version
• OS Product Type
• OS Build
• OS Architecture
• IPv4 Address
• Bot Version

Stolen Information

This Backdoor sends the gathered information via HTTP POST to the following URL:

• https://drive.{BLOCKED}content.kz/drive/info

Other Details

This Backdoor connects to the following URL(s) to check for an Internet connection:

• http://www.w3.org/1999/XSL/Format

It connects to the following possibly malicious URL:

• http://{BLOCKED}.{BLOCKED}.8.8/{random string}

It does the following:

• It will not execute its malicious routines if any of the following is not satisfied:
  • year is 2019
  • file extension of running malware process is .ocx
  • malware process is running as regsvr32.exe

It deletes itself after execution.

It adds the following scheduled tasks:

• Task Name: {random characters}
• Trigger: At system boot; executes indefinitely
• Action: cscripT /B /e:jsCript {filename of JavaScript file}.txt