Safety Instruments Testing: Spotting and Stopping Process Attacks

This report analyzes security weaknesses in HART-enabled field instrumentation that allow sensors to be placed into 'fixed' or 'loop' current modes—either maliciously or accidentally—causing analog readings to be inaccurate and potentially blinding Safety Instrumented Systems. It documents monitoring challenges across multiple proprietary communication paths, demonstrates a practical defense by using HART-aware I/O to read the device status bit and trip safety logic when instruments report non-trustworthy analog output, and provides vendor- and engineering-focused mitigation recommendations.