When the hell was this first written?
NT 4.0? "Deterministic, hard real-time operating system"? Huh? "The PLC is fundamentally a box or computer with a processor. "???
The article is dated March 2007 but if this is recent and a legit take then it shows exactly what we have to worry about, albeit unintentionally.
Don't get me wrong there is a place in many industries for properly developed "PC based" systems (whether Windows Linux or other OS) to directly control processes but I have to wonder if the author of this ever developed and implemented a truly complex integrated control environment.
Woefully uninformed and simplistic.
I have to assume this was written years ago and just dug up or perhaps relabeled. If so it shows how we got to where we are from a security perspective in the SCADA and DCS world. If not it shows very well how far we have to go.