Almost every Linux security incident eventually traces back to a permission or privilege decision: a file too readable, a script too writable, a command too freely elevated. The permission model — owner, group, and others, each with read, write, and execute bits — is the foundational access-control layer beneath every Linux service, and the sudo model governs the single most consequential decision on any system: who can temporarily become root, and for exactly which commands. Mastering both is the entry point to everything else in Linux hardening.
Analogy🏏Cricket
💪 Think of it like fitness: injuries follow a predictable chain — poor warm-up, then form breakdown, then compensation, then the actual tear — and a good physio catalogs where each patient's chain can be interrupted early, rather than only treating the tear afterward. MITRE ATT&CK is the sports-medicine literature of intrusions: a public catalog of every observed breakdown pattern, organized by the stage it serves — how attackers get in, how they escalate, how they extract. Coaches worldwide describe an athlete's risk in that shared vocabulary. This reveals ATT&CK's real value: intrusions become a sequence you can interrupt at stage two, not a disaster you discover at stage five.