# Pressure Baseline Drift Rules **R5** and **R5b** track how far a process pressure signal has drifted from its established baseline. This is the single most discriminative check in the kernel's [[Detection Rules|rule set]]. > [!success] Separation power > - **SWaT:** anomalous vs. normal separated by **1,262×** > - **HAI 21.03:** separated by **1,188×** > > A three-order-of-magnitude margin means the signal is not a marginal statistical edge — it is a structural tell of a compromised or failing process. The reason it works is physical: pressure baselines in water and process systems are tightly governed by [[The OT Intelligence Layer|physics and equipment state]], so genuine drift is rare and meaningful, while spoofed or manipulated control reliably perturbs it. This is why the kernel leans on engineered, physics-grounded predicates rather than generic statistical outlier scores. Per-site baselines (the constants R5/R5b compare against) are supplied through [[Profile-Based Portability]]; the comparison logic itself is fixed in the [[Common Trust Core]]. --- Related: [[Integrity Kernel MOC]] · [[Detection Rules]] · [[Cross-Domain Validation]] · [[The OT Intelligence Layer]]