Cyber Security
From first principles of trust and cryptography to attacking and defending real systems.
Foundations
3 lessonsWhat security actually protects
Before any tool or attack, security is about three goals — confidentiality, integrity, availability — and a habit of thinking like an attacker.
Start lessonHashing — a fingerprint for data
A hash turns any data into a short, fixed fingerprint that changes completely if the data changes at all — and can't be run backwards. It underpins integrity checks and password storage.
Start lessonKeys, and how strangers share a secret
Encryption needs a shared key — but how do two strangers agree on one over a channel everyone can see? Public-key ideas make the impossible routine.
Start lessonCore
3 lessonsTLS — how the padlock works
Every https:// page runs on TLS, which combines the Foundations primitives — key exchange, certificates and symmetric encryption — into a secure channel. Here's the whole handshake.
Start lessonAuthentication — proving who you are
Passwords, hashing at scale, multi-factor auth and session tokens — how systems verify identity, and the many ways that goes wrong.
Start lessonWeb vulnerabilities — how attackers get in
Most breaches don't break the cryptography — they exploit the application. Injection, XSS and broken access control, and the one habit that defends against them.
Start lessonAdvanced
2 lessonsThinking like an attacker
Real attacks aren't a single magic exploit — they're a campaign with stages. Learn the attack lifecycle and you learn where defenders get to intervene.
Start lessonNetwork security — attack and defend
The network is the battlefield attackers cross. Man-in-the-middle, denial of service and the defences — firewalls, segmentation and zero trust — that shape the fight.
Start lessonExpert
2 lessonsDetection and incident response
Prevention fails eventually, so mature security assumes breach: detect fast, respond calmly, recover cleanly. Meet logging, SIEM, the SOC and the incident lifecycle.
Start lessonThe human layer — the real front line
The strongest cryptography is undone by a convincing email. Social engineering, security culture, and why the best defenders treat people as the primary attack surface.
Start lessonStay in the loop
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