Part of Langner's point is that if you can insert code into the PLC, which Stuxnet shows you how to do, you don't need any insider information to create a damag

Part of Langner's point is that if you can insert code into the PLC, which Stuxnet shows you how to do, you don't need any insider information to create a damaging payload. Just stop the PLC from running after a given date, or for thirty seconds every half hour, or whatever. The PLC is there for low-level, real-time control of actuators that direct some physical process, and once the control stops, the process will go on in some unwanted way. Of course there are safeguards to prevent catastrophes, but even stopping some part of the automation in an industrial plant could easily cause serious problems such as damaged equipment and downtime for debugging.