This Halloween special of the Small Business Cyber Security Guy peels back the curtain on the scariest place hackers hide: the tools and toolchains you trust. Hosts Graeme Falkner, Noel Bradford and Mauven MacLeod go ghost hunting inside compilers, build systems and update pipelines to show how supply‑chain attacks can insert backdoors that you’ll never spot by reading source code alone. The episode revisits Ken Thompson’s classic compiler backdoor thought experiment and explains, in plain language, how a compromised compiler can propagate secrets invisibly. The hosts walk through real incidents — XcodeGhost, SolarWinds, EventStream, and Log4j — to demonstrate how attackers target development tools and upstream suppliers to compromise software at scale. Expect practical, small-business-focused anecdotes (including a midnight accounting patch that wreaked havoc) and clear explanations of why technical debt, single-developer codebases, and blind trust in update pop-ups are dangerous. The conversation highlights how even open-source software can be compromised if maintainers or dependencies are compromised. The episode also covers defences and takeaways: demand provenance and supply-chain transparency from vendors, insist on reproducible builds where possible, use two-person reviews and well-maintained dependencies, and protect access with strong authentication. The hosts debate how to distribute trust, verify your verifiers, and reduce single points of failure so one compromised supplier or contractor can’t haunt your whole business. There’s a sponsor segment from Authentrend about passwordless biometric sign-ins as a way to block credential-based intrusions, along with links to resources and a trial, in the show notes. Throughout, the hosts balance technical history and horror stories with concrete steps small businesses can take now to keep their compilers and supply chains clean. Listen for clear, actionable advice for small businesses, including how to ask vendors the right questions, when to bring in trusted IT partners, and simple measures to keep the lights on and the doors locked against the ghosts in your code. Sláinte — and may your backups never rise from the grave.