Overview
Your complete guide to The protective tools
Linux and the command line for defenders, cryptography with a live SHA-256 demo, web application security with the OWASP Top 10, and system and network security: hardening, segmentation and zero trust.
Non-technical and technical learners alike. Every part opens two ways in: a plain path built on an analogy for someone starting from zero, and a detailed path for someone who knows the basics and wants depth.
An animation, then what you need before you start, then the idea with code you run, then a worked example, then review cards and "test your understanding" questions.
Do not leave a part before you can answer its questions without guessing. Reading alone proves nothing.
Pick a topic
A look at The protective tools
You start with the terminal every security tool runs on, then learn how secrets stay secret, then how web apps are broken and protected, then how to harden systems and networks.
| Part | Topic | You learn |
|---|---|---|
| 1 | Linux and the command line for defenders | The file tree, permissions and sudo, users, where logs live, grep, awk, sort and uniq, processes and ports, pipes |
| 2 | Cryptography: how secrets stay secret | Symmetric and asymmetric, hashing and the avalanche effect, digital signatures, TLS and PKI, post-quantum |
| 3 | Web application security: the OWASP Top 10:2025 | The OWASP Top 10:2025, broken access control, injection and parameterised queries, the software supply chain, failing safe |
| 4 | Systems and network security: hardening, segmentation and Zero Trust | Vulnerability management and CISA KEV, hardening, segmentation, Zero Trust, EDR, backups, shared responsibility |
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