LESSON 11

Defensive Security

Learning objective: Understand layered defence and everyday protections.

Understand

Defensive security is about reducing risk with layers.

No single control is perfect, so defenders use layers: updates, backups, MFA, least privilege, and monitoring. If one layer fails, others still protect you. Regular backups also defend against ransomware and mistakes.

Analogy: Layered defence is like a castle with a wall, a moat, and a locked gate — not just one barrier.

See It in Action

A personal defence stack:

Updates + MFA + Backups + Least privilege
How it works: Stacking simple protections means an attacker must defeat several layers, not just one.

Try It Yourself

  1. Turn on automatic updates somewhere.
  2. Set up one backup.
  3. Remove an admin right you do not need.

Quick Quiz

What is the idea behind layered defence?

Challenge

Set up two protective layers on a device and describe how they help.

Success condition: You have at least two defensive layers active on a device.