Some History of Security Levels in ISA/IEC 62443

One of the comments/complaints I’ve heard often about the ISA/IEC 62443 series is that the definition of Security Levels (SLs) is too vague and can’t be used. Many of these comments come from people that are either safety engineers or have worked around inside and/or safety systems for long periods of time. Now that 62443-4-2 …