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Cybersecurity from zero

Thirteen lessons that take you from no background to the basics a junior defender uses every day: what security protects, passwords and two-factor sign-in, phishing, malware and backups, encryption and hashing, access control, firewalls and segmentation, web app flaws like SQL injection, patching, reading logs, handling an incident, and ranking risk. Written for defenders: each attack is explained just far enough to spot and stop it.

  1. Before you start

    The computer and network words the course uses, and how to read its short Python examples.

    6 questions

  2. What security protects

    Confidentiality, integrity and availability, and how assets, threats, vulnerabilities and risk fit together.

    7 questions

  3. Passwords and signing in

    Why long unique passwords, password managers, two-factor sign-in and passkeys stop most account takeovers.

    7 questions

  4. Phishing and social engineering

    How scam emails, texts and calls trick people, the red flags to look for, and what to do when one arrives.

    6 questions

  5. Malware, ransomware and backups

    Viruses, worms, trojans, spyware and ransomware, how they get in, and why tested offline backups beat paying.

    6 questions

  6. Encryption and hashing

    Symmetric and public-key encryption, hashes, salts and signatures, and where each one protects your data.

    7 questions

  7. Access control

    Least privilege, roles, separate admin accounts, removing access when people leave, and the idea of zero trust.

    6 questions

  8. Defending a network

    Firewalls, closing ports, splitting the network into segments, VPNs, secure Wi-Fi and safe remote access.

    6 questions

  9. Web app security

    Injection, cross-site scripting, broken access control and the coding habits that prevent them.

    6 questions

  10. Vulnerabilities and patching

    CVEs and severity scores, knowing what you run, deciding what to patch first, and software you depend on.

    7 questions

  11. Logs and detection

    What logs record, gathering them in a SIEM, reading sign-in logs, alerts and false positives.

    7 questions

  12. Incident response

    What to do when something goes wrong: prepare, find out what happened, contain it, clean up, recover and learn.

    6 questions

  13. Risk, frameworks and the law

    Scoring risk, the four ways to treat it, the NIST Cybersecurity Framework, staying legal and where to go next.

    7 questions
More info

How it works

Each lesson is a short read with examples, then a few practice questions. Some ask you to type an answer (a number, an address, what a piece of code prints), some have you pick one, and some have you tap steps or lines into the right order. You can try again as often as you like; after two misses there’s a button to show the answer.

What do I need to know first?

Nothing. The first lesson explains the computer and network words the rest uses, and how to read the few short Python examples (you only need to read them). The networking and Linux courses go deeper if you want them.

Related courses

Where is my progress saved? In this browser, like the rest of the site. Nothing to sign up for.

“Python” is a registered trademark of the Python Software Foundation. This course isn’t made by or affiliated with it.

For learning and defending your own systems. Only test systems you own or have written permission to test: getting into anyone else’s is a crime in most countries, whatever the reason. Every company, person and address in the examples is made up.