How to Build a 404 page not found C2

This report demonstrates a proof-of-concept covert C2 technique that embeds base64-encoded commands inside HTML comments on HTTP 404 (File Not Found) pages; the author details server configuration, a client that detects 404 responses, decodes and executes commands on Windows/Linux, and a simple listener to receive command output, with a demo showing remote file creation. The write-up references prior research and provides source code links, emphasizing that the technique is stealthy and easily overlooked by typical 404 monitoring but requires initial compromise or control of a web server.