How attacks work, and how to stop them

Every break-in, from a stolen password to a hijacked slice of the internet, exploits a gap between what a system assumes and what is actually true. This site is a visual, hands-on guide to those gaps: where they come from, how defenders close them, and how to tell when someone is probing yours.

It is written for the defender. You will see how flaws arise, through harmless examples, and spend most of your time on the fixes: the cryptography, the protocols, the coding habits and the monitoring that make attacks fail. It builds on networks.jelia.nyc; each chapter links to the networking chapter you may want to read first. When you want the hands-on version for your own machines, RedPatch is the practical side: sourced security tips and tools for macOS, Windows, Windows Server and Linux, plus a daily security news feed. This site explains why each of those steps matters.