Ralph Langner heads Langner, an independent cyber-security firm that specializes in control systems -- electronic devices that monitor and regulate other devices, such as manufacturing equipment.

These devices' deep connection to the infrastructure that runs our cities and countries has made them, increasingly, the targets of an emerging, highly sophisticated type of cyber-warfare.

And since 2010, when the Stuxnet computer worm first reared its head, Langner has stood squarely in the middle of the battlefield.

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