Three years after the 2010 discovery of the Stuxnet attack that sabotaged a uranium enrichment process at the Natanz nuclear facility in Iran, researchers at Symantec found what they surmised was a precursor to the known payload that caused the plant’s centrifuges to spin out of control and fail. This early version of Stuxnet, which they called Stuxnet .5, targeted the Siemens PLC control systems that operate the valves that feed uranium hexafluoride gas into uranium enrichment centrifuges.

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