The industrial controllers were not connected to the internet. Part of Stuxnet's sophistication was crossing the air gap via USB sticks that were infected throu

The industrial controllers were not connected to the internet. Part of Stuxnet's sophistication was crossing the air gap via USB sticks that were infected through two never-seen-before 0-day attacks, the infamous shortcut icon attack vector, and autorun trojans. Why were the control systems running Windows? Because it has a GUI. This helps when monitoring control systems, and of course is the only platform Siemens' monitoring systems run on.