Let’s Build a Multi-Modal C2 Covert Channel in Golang

Overview

Below are the lecture notes for my AntiSyphon workshop presented September 18, 2025. Though the notes are in general more descriptive than the actual lectures, they are not expanded, meaning the content from the lectures roughly map 1:1 onto these notes.

Solutions

All the final solutions are available on GitHub here. You’ll find a copy of the complete slides, as well as the lectures available here in markdown format.

Foundation

• Setup Guide
• Project Structure and Interfaces
• YAML-based Configuration Management System

HTTPS Implementation

• HTTPS Server
• HTTPS Agent
• HTTPS Loop

DNS Implementation

• DNS Server
• DNS Agent
• DNS Loop

Transition Using API Switch

• Implement API Switch
• Dual-server Startup
• Agent Parsing + Protocol Transition