Backdoor Botfly

A tailgating tool for authorized security testing, training, and research.

Backdoor Botfly deployed on a door frame, tail hanging into the gap

The Story

I built a prototype of this tool back in 2024, but it was over-engineered and a little too expensive for what it was. So I sat on the idea for two years.

In early 2026, Alex Cole released his FIT'D and LIFT'D tactical doorstops. After getting real-life field experience with his products, I confirmed they abided by the US Navy's KISS principle (Keep It Simple, Stupid). A few weeks later I took a training with Alex and afterwards asked if he would be willing to discuss an idea I had. One quick 30-minute call and the Backdoor Botfly was redesigned.

That redesign, while useful, ultimately involved more user input than I wanted — especially if the door wasn't aligned, for example a sagging door. You can find a copy of that version on my GitHub: FOSS Backdoor Botfly.

So I redesigned it again. This version uses three pieces — the Backdoor Botfly, 3M VHB tape, and gear ties — with an optional fourth item, shrink wrap.

I brought that version to DEF CON 34 and sold 80 prototypes — with no marketing.

The Concept

The Backdoor Botfly is a tailgating tool designed to be used on doors where the hinges are exposed to you. This can be both interior and exterior doors.

Start by peeling off the 3M VHB tape and placing the Backdoor Botfly on the door frame above the door, on the side opposite the hinges. I've had better success making the Backdoor Botfly's tail hook-shaped, as seen in the pictures below.

Backdoor Botfly tail, shown against a ruler for scale Backdoor Botfly with a hook-shaped tail, shown against a ruler for scale

As soon as the door opens, while a person is exiting, the Backdoor Botfly's tail will drop into the space the door previously occupied.

Assuming the person does not see it, as the door closes it will catch the Backdoor Botfly's tail, which buries itself between the door and door frame, ultimately preventing the door from securely closing.

Backdoor Botfly's tail jammed between the door and frame

Optionally, you can use heat shrink to make the Backdoor Botfly's tail match the color of the door or frame.

Due to the nature of this device, we recommend not using it on the main door but rather a smokers' exit, side exit, or back door.

Variants

Backdoor Botfly

Inexpensive, semi-disposable tailgating tool.

Pricing & Availability

More details coming soon.

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Backdoor Botfly is intended solely for authorized physical security testing, training, and research.