Re: "Who left that microUSB charger cable lying around?"
In 2008, a handful of USB flash drives were liberally sprinkled around the US CENTCOM parking lot. It only took one system administrator saying, "Cool, look what I found!" and plugging it into a misconfigured system (out of tens of thousands, as autorun wasn't disabled) and the rest is history. Every network, classified and unclassified was infected (again, due to non-adherence to both best practices and codified law).
Cost to clean up the mess? One billion dollars for the first incident. A month later, it was rinse and repeat, as a proper baseline *still* wasn't adhered to by the contractors.
The cost of recovery for incident 2 remains classified at levels much the same as nuclear warhead design plans.