Fig. 8
From: Detecting stealthy attacks against industrial control systems based on residual skewness analysis
Detection of the variant of surge stealthy attacks. When the variant of surge stealthy attacks in (b) and (e) are conducted on the water level control system and the pH value control system, respectively, the real water level shown in (a) deviates significantly from the seemingly normal but compromised water level, and the real pH value shown in (d) also deviates observably from the seemingly normal but compromised pH value. The significant changes of skewness coefficients of residuals shown in (c) and (f) indicate that the approach proposed can identity the variant of surge stealthy attacks effectively