For those of us who don't do industrial process control, what would that do to the plant?
Supposedly more than 30 programmers worked on Stuxnet. That seems like a big investment just to increase the wear rate on a few motors, however critical they might be.
I have no clue what it would do. My guess was that you'd want to not just disrupt production, but preferably damage the equipment. Since the centrifuge is such a delicately built device (see wikipedia: http://en.wikipedia.org/wiki/Zippe-type_centrifuge), exciting a resonance or causing a bearing rub would be a productive hack.
Maybe flipping the motor drive frequency from 1200Hz to 2Hz and back could act like an impulse to excite any high-Q resonance in the centrifuge structure?
The description in the article suggests the virus quickly drops and restores the speed of the motor. A guess (from someone who knows nothing about nuclear facilities) would be perhaps this would result in enrichment processes failing to sustain the chemical process, but in a manner that would be relatively hard to detect since it the change in speed is only over a short time period.
Most people seem to be assuming the intent is either to damage the centrifuges or stop them from working in other obvious ways. However, that would just lead to them being replaced, probably with better protection from reinfection.
I think there is another option: these modifications in the frequencies were intended to make sure the uranium did not becoming pure enough, effectively preventing Iran from obtaining a working bomb. If the virus wasn't discovered, it could have taken the Iranian scientists years to figure out why the centrifuges weren't doing their jobs, after discovering the lack of purity in the first place.
For those of us who don't do industrial process control, what would that do to the plant?
Supposedly more than 30 programmers worked on Stuxnet. That seems like a big investment just to increase the wear rate on a few motors, however critical they might be.