A fortress‑style system is all about layers and fail‑over. First you lock the perimeter with a robust firewall and intrusion‑prevention that only lets known, authenticated traffic in. Then you layer in application‑level checks—rate‑limits, input sanitisation, and anomaly detection—to catch attacks that slip past the first gate. On the physical side, embed sensors that monitor temperature, vibration, and access points, feeding data into the same central analytics engine. If something looks off, you trigger automated lockdowns: cut power to non‑essential circuits, isolate compromised nodes, and alert the ops team. Keep each layer independent so a breach in one doesn’t cascade to another. That’s the core of a cyber‑physical defense that’s as solid as a fortress.