Teach cyber security the way it really works with this visual, colourful, ready-to-teach PowerPoint lesson for Year 9 Computing. Pupils meet malware, phishing and other social engineering, then see why password length beats clever substitutions with simple exponent calculations. The deck covers firewalls, encryption, two-factor authentication and updates as layers of defence, includes a hands-on Caesar cipher, and explains ethical hacking and the Computer Misuse Act 1990 so pupils understand the line between curiosity and crime. A spot-the-phish slide and a password challenge use invented examples only. Two interactive activities ask pupils to design a school security plan and justify their choices, with explain-why questions for extra challenge. Speech-bubble prompts nudge rather than gush. The tone treats pupils as capable young people, using real terminology such as ransomware, credential stuffing and penetration testing, and every slide keeps to one clear idea. It is non-specialist friendly, ideal as a cover lesson, and builds towards GCSE Computer Science. 18 slides, about one hour, aligned to the KS3 National Curriculum.