morphovar forwards a writeup in Low-tech Magazine recounting an almost-forgotten predecessor to email and packet-switched messaging: the optical telegraph
. The article maps out some of the European networks but provides no details of those built in North America in the early 1800s. Man-in-the-middle attacks were dead easy. "More than 200 years ago it was already possible to send messages throughout Europe and America at the speed of an airplane — wireless and without need for electricity. The optical telegraph network consisted of a chain of towers ... placed 5 to 20 kilometers apart from each other. Every tower had a telegrapher, looking through a telescope at the previous tower in the chain. If the semaphore on that tower was put into a certain position, the telegrapher copied that symbol on his own tower. A message could be transmitted from Amsterdam to Venice in one hour's time. A few years before, a messenger on a horse would have needed at least a month's time to do the same."