What Is EvilDuck S3 and Why Build a Rubber Ducky DIY?
EvilDuck S3 is an open-source USB keystroke injection device that behaves like a standard keyboard while running scripted commands at high speed, making it useful for penetration testing, security research, and repeatable automation on desktop systems. Unlike commercial options, EvilDuck S3 is designed as a rubber ducky DIY platform that you can build, modify, and program yourself using widely available microcontrollers. The project began as a custom PCB around an ATmega32U4 that emulated a keyboard from an SD-based script, then evolved into a more capable design with WiFi and a web interface. The latest EvilDuck S3 revision replaces the two‑chip architecture with an ESP32-S3 that handles both USB HID and WiFi, freeing space for features like MicroSD storage and status LEDs. Because the hardware and firmware are open source, you keep full control over payloads, networking, and future ESP32-S3 projects.
Choosing Your Hardware: ESP32-S3 or Arduino-Style Boards
To build an EvilDuck-inspired USB rubber ducky, you have two main routes: a custom ESP32-S3 board like EvilDuck S3, or an Arduino Micro–style board based on ATmega32U4. ESP32-S3 is the more flexible choice for ESP32-S3 projects because it combines native USB HID with WiFi in a single chip, cutting out the need for a second microcontroller and any inter-chip communication. According to CiferTech, “The answer was the ESP32-S3. It handles both USB HID and WiFi natively on a single chip.” His EvilDuck S3 PCB adds a MicroSD card slot for payload storage, an addressable WS2812 RGB LED as a status ‘eye’, a 5V-to-3.3V regulator, USB Type‑A connector, and indicator LEDs on RX/TX lines. If you already have Arduino Micro or similar boards, you can still follow the same concepts, but you will likely need a separate WiFi module and a slightly different firmware stack.
Assembling the Hardware: From USB Plug to SD Storage
Start your rubber ducky DIY build by planning how the board will connect and power itself over USB. In EvilDuck S3, the USB Type‑A connector routes its data pins directly to the ESP32-S3, so the same port is used both for programming and for USB keystroke injection on target machines. A regulator such as an LM1117 steps the 5V USB line down to 3.3V for the ESP32-S3 core. Add a MicroSD card slot to expand script storage beyond internal flash; note that CiferTech’s early revision missed the SD detect pin, later fixed in the GitHub files, so follow the updated schematic. On the front side, place the WS2812 RGB LED where it is clearly visible to give color-coded status feedback. Optional RX/TX LEDs provide a quick activity glance while the device is communicating or being flashed from your development computer.
Flashing Firmware and Writing DuckScript Payloads
With the hardware ready, the next step is firmware that turns your ESP32-S3 or Arduino-compatible board into a USB keystroke injection tool. EvilDuck S3 firmware exposes the ESP32-S3 as a standard HID keyboard, so most systems require no extra drivers. At boot, the device can start a WiFi access point and launch a web interface where you upload, edit, and delete scripts. These payloads are written in DuckScript, a line-by-line language that the interpreter converts to keyboard signals in real time. Scripts are stored in SPIFFS flash by default, with optional transfer to and from the MicroSD card through the browser interface. The firmware also supports an autorun feature: you can mark a script to execute automatically when the device is plugged into a host. USB mass storage mode lets you manage files with drag-and-drop tools if you prefer desktop workflows.
Use Cases, Safety, and Extending Your Open Source Security Tool
Once your DIY rubber ducky is running, you can apply it to repeatable penetration testing tasks and time‑saving automation. Typical security scenarios include opening shells, pulling basic system information, or launching browser-based checks using prewritten DuckScript payloads for Windows, Linux, or macOS. The web interface offers live execution status, logs, and the ability to send single commands for rapid testing, which makes EvilDuck S3 a flexible part of a wider toolkit of open source security tools. Use it only on systems you own or have explicit permission to test, and document your payloads clearly so they remain auditable. Thanks to the ESP32-S3 platform, you can extend the project with features like hidden SSIDs, custom authentication, or new storage workflows. As CiferTech notes, the hardware is considered complete, while the firmware is designed to keep evolving alongside the community.
