EchoLink C2 Framework 🛡️

A custom, lightweight Command and Control (C2) framework designed to demonstrate asynchronous communication between a central web dashboard and native Windows C++ agents.

Disclaimer: This project was developed strictly for educational purposes, security research, and authorized testing. Do not use this software on systems where you do not have explicit permission.

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🚀 Features

• Asynchronous C2 Architecture: Implements a pull-based beaconing mechanism, eliminating the need for open ports on the target machine.
• Native Windows Agent: Written in C++ utilizing the native WinHTTP API for stealthy, low-level network communication.
• Secure Operator Dashboard: A Vanilla JS Single Page Application (SPA) secured with JSON Web Tokens (JWT) to prevent unauthorized access.
• RESTful Python Backend: Built with Flask and SQLAlchemy (SQLite) serving as the central State Machine and data broker.
• Real-Time Terminal UI: Features a dynamic, auto-scrolling terminal interface for executing commands and viewing outputs seamlessly.

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🧠 Architecture Overview

The framework operates on a decoupled architecture, ensuring the operator and the target never communicate directly:

1. The Agent (C++): Runs on the target Windows machine. It registers itself with the server and periodically polls (beacons) the /tasks/<agent_id> endpoint to retrieve pending commands.
2. The Server (Python/Flask): Acts as the intermediary. It validates operator JWTs, stores commands in the SQLite database as pending, and updates them to completed once the agent posts the execution results back.
3. The Dashboard (JS/HTML): The operator's interface. It continuously polls the secure API to provide a real-time view of online agents and their execution history.

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🛠️ Tech Stack

• Backend: Python 3, Flask, SQLAlchemy, PyJWT
• Frontend: HTML5, CSS3, Vanilla JavaScript (Fetch API)
• Agent: C++, Windows API (WinAPI), WinHTTP
• Database: SQLite

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⚙️ Getting Started

Prerequisites

• Python 3.8+
• Visual Studio 2019/2022 (with C++ Desktop Development workload)

1. Server Setup

Clone the repository and set up the Python environment:

git clone https://github.com/hananelk26/EchoLink-C2-Framework.git
cd EchoLink-C2-Framework/Server

Install required dependencies

pip install flask flask-sqlalchemy pyjwt

Run the C2 Server

python app.py

The server will initialize the SQLite

database automatically and listen on http://0.0.0.0:5000.

2. Agent Compilation

1. Open Agent.sln in Visual Studio.
2. Set the build configuration to Release | x64.

Note: Ensure the IP address in the Agent.cpp WinHTTP configuration matches your C2 server's IP.

3. Build the solution. The compiled .exe will be generated in the x64/Release folder.

💻 Usage

1. Open your web browser and navigate to http://localhost:5000.
2. Log in using the default operator credentials (configurable in app.py).
3. Execute the compiled C++ Agent on a Windows machine.
4. The agent will appear as Online in the left sidebar.
5. Select the agent and use the terminal interface to send standard Windows CMD commands (e.g., whoami, ipconfig, dir).

🔒 Security Considerations

Currently, the agent communication is performed over standard HTTP (Plaintext). Future iterations will include XOR-based payload encryption and HTTPS (TLS) support for evasion and secure transit.