Supposedly, Stuxnet was using not just one, but four XP zero-day exploits that allowed it to spread from computer to computer, typically via USB sticks. Lots of predators jumped into the fray offering XP users tools to clean their systems with. Mostly at a price, of course. But only Siemens systems were under attack. Warnings went out to not just remove it from Siemens systems as the PLC code might still contain hidden commands. Advice was to restore the system from a secure backup. Next, more people jumped in to warn us all about the upcoming cyber wars.