Even on a dry day, the MTA's 300 pumping rooms remove an estimated 13 million gallons of water from the tunnel network, just to keep the system dry enough to run.

WSJ: Salt Water Puts City's Subway System 'in Jeopardy'

And traffic between geographically separated company networks can be routed through a virtual private network (VPN) tunnel instead of being exposed to the open Internet.

CNN: Analysis: Linux security

Once it is plugged in to the network behind the router it creates an SSL tunnel back to head quarters.

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