Ai

Capchan – Solving CAPTCHA with Image Classification

13 March 2025 ~25 min By Adriaan Bosch
Ai Ctf Neural-Nets Tool
A few years ago, I tried my hand at the, now retired, CAPTCHA Forest CTF, which was part of the nullcon HackIM 2019. I wanted to solve it using computer vision and machine learning. This started me on a path of discovery and incremental improvements that finally resulted in capchan, a generic CAPTCHA to text tool. This post is broken into four parts: The first CTF The second CTF Neural Network Fundamentals Creating capchan ATTEMPT_ZERO Starting the CTF – I connected to the netcat instance, but after staring at hexadecimal, I immediately closed it and moved on to try another CTF.