Hidden HID v2 is a tiny, creator-designed USB Type-A device that presents as a keyboard and injects keystrokes. Its PCB sits inside the connector rather than protruding from the port; infrared phototransistors serve as both spacers and a line-of-sight on/off control. The project documents a basic “hello world” firmware example, not a general-purpose payload library or a Hak5 USB Rubber Ducky feature set.
What Hidden HID v2 is—and what “Rubber Ducky” means here
Emma’s project uses an STM32 microcontroller to make a USB device act as a human interface device (HID), the class commonly used by keyboards. In this case, the device can send keystrokes to the connected computer. “Rubber Ducky” is often used colloquially for this category of keystroke-injection device, but Hidden HID v2 is a separate project from Hak5’s commercial USB Rubber Ducky.
Hak5 documents its own product’s HID mode and DuckyScript language; those product-specific features should not be assumed to apply to Hidden HID. The project’s repository documents its own hardware and a small firmware example instead. Hak5 USB Rubber Ducky documentation
How it fits inside a USB-A port
The design is a single small PCB with its components beneath the USB contacts. Emma describes the idea as making use of unused space inside a USB connector. As quoted in Gareth Halfacree’s Hackster.io report, Emma said: “With the increasing miniaturization of components, it was quite easy to design a basic USB-enabled microcontroller circuit that fits inside the 2.5mm available.”
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The project page reports a total thickness of 2.2 mm: 1.8 mm for the phototransistors and 0.4 mm for the PCB. That is the creator’s design dimension, not an independent measurement. The parts also help hold the board snugly in the port. The author identifies the main components as an STM32, an LDO regulator and four infrared phototransistors. Hidden HID v2 project page
What changed in v2
The creator describes two notable revisions:
- Programming: v2 removes the SWD programming pins and uses the STM32’s internal USB bootloader.
- Activation and spacing: The earlier electrically inactive LED spacers were replaced by IR phototransistors. These components still act as spacers, but also provide a simple optical on/off control.
The project does not establish a radio link or arbitrary-distance remote control. Activation depends on an infrared signal reaching the phototransistors, so it is a line-of-sight arrangement. Hidden HID GitHub repository
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- Package includes:1 x Virtual Keyboard Module,1 x Pin Header
How programming is documented
According to the creator’s instructions, the BOOT0 test pad selects between application mode and bootloader mode. The documented workflow is:
- Bridge the middle BOOT0 test pad to GND to select application mode, or to 3V3 to select the bootloader.
- Connect the device over USB while it is in bootloader mode.
- Use STCubeProgrammer to download a hex file.
- Select application mode by tying BOOT0 to GND when you want the board to run its firmware.
This is the creator’s described procedure, not an independently tested programming guide. The repository places KiCad design files in /KiCad, Gerbers and the bill of materials in /Fabrication, and firmware in /STM32. It notes that some paths in the sample may need adjustment. Project files and firmware
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What the sample firmware demonstrates
The repository calls its example “basic test firmware.” It waits for an IR signal, opens a terminal and echoes “hello world.” That illustrates the project’s basic combination of optical triggering and keyboard-style input; it does not demonstrate compatibility across operating systems, a tested deployment flow, or a collection of ready-made attack payloads.
Practical limits: the occupied port and manual removal
The board sits inside the USB-A connector, so it occupies that port. Hackster’s report notes that another USB device cannot be inserted while Hidden HID is present. The project page describes removal with a thin plastic tool hooked around the phototransistors. Emma also mentions using a broken plastic tweezer as an improvised workaround; the report does not present it as an included accessory.
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Build files and board availability
The repository links to a PCBWay community listing where the creator says a bare or assembled PCB can be ordered. That listing is a route to boards, not evidence of current stock, pricing, shipping destinations or exactly what an assembled board includes. Although the design files are publicly linked, Hackster describes the license as unspecified; a public repository alone does not establish permission to reuse or redistribute the design. Check the repository’s current license files and the listing’s current terms before building or ordering.
How Hidden HID v2 differs from a commercial USB Rubber Ducky
The two share the broad idea of using USB keyboard behavior to inject keystrokes, but the available documentation does not make them feature-equivalent.
| Question | Hidden HID v2 | Hak5 USB Rubber Ducky |
|---|---|---|
| Physical form | Designed to sit inside a USB-A port; the occupied port cannot take another device at the same time. | The cited Hak5 documentation establishes a commercial product, but does not establish an equivalent inside-the-port form. |
| Activation | Creator describes IR phototransistors as a line-of-sight on/off control. | The cited documentation describes HID mode; it does not establish the same IR control. |
| Programming or scripting | Creator documents the STM32 USB bootloader workflow and a basic test firmware example. | Hak5 documents its own DuckyScript language; that does not establish support in Hidden HID. |
| Price and current availability | Current price and availability are not established by the project sources. | Current price and availability are not established by the cited documentation. |
For Hidden HID’s board and firmware details, see the project repository; for Hak5’s own product documentation, see Hak5’s documentation.
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