Preface
Preface
Who this course is for
This course is for individual users, freelancers, small-business owners and technical people who want to manage their own digital lives sustainably. You do not need to be a security expert. You only need a few important accounts (email, banking, cloud storage), some data you do not want to lose, and to have started using AI assistants at work.
Why this course exists
Most security material teaches you how to lock the door tightly: strong passwords, two-factor authentication, watching out for scams. That is right, but not enough. Many people lose accounts and data not because they were attacked, but because they locked themselves out: the 2FA codes lived on the very phone that was just lost, the recovery email of one account needs another account to get in, the "backup" was really just a synced folder that got deleted along with everything else.
This course teaches a different way of thinking: design your system to survive when many things fail at once, even when the thing that fails is you. Since 2025–2026, as AI assistants started reading email, organizing files and running commands on users' behalf, this mindset matters even more: AI works fast, so it also breaks things fast if given too much power.
How to use this course
- Each chapter contains: Learning objectives, Concepts, Worked example (a hypothetical character "Mr. A" with the sample domain example.vn), Common mistakes, Checklist, Exercises and Summary.
- Study in order. Chapters 1–2 are the foundation; every later chapter returns to the 4-tier model.
- Do the exercises on paper or in a separate notes file. Never write passwords, PINs, recovery codes or secret keys in the exercises. Only write where a secret is kept.
- Product names (password managers, NAS, cloud services…) are only examples to help you picture things, not advertising. The principles apply to any equivalent product.
Conventions used in this course
| Symbol | Meaning |
|---|---|
| Mr. A | Hypothetical character used throughout the examples |
| example.vn, example.com | Sample domains, not real domains |
| *** | Personal information that has been hidden |
| [ ] | A checklist item to tick when done |
| ROOT, CORE, BRANCH, LEAF | The four tiers of the anti-lockout model (Chapter 2) |
The question running through this course: "If I lose this, do I still have a way back?" If you cannot answer yet, do not turn on any more security layers until you can.