The security problem arose because 25 years ago, the Internet was tiny and
relatively private. Today it is enormous and truly public. As the Internet has grown,
the need for security has grown with it. Consider that TCP/IP and the early Internet
precursors were developed as very small networks used by government researchers
at the United States Defense Advanced Research Projects Agency (DARPA or ARPA).
People who were well known and would generally have had security clearance
controlled all the hardware. In such a network, you don’t need to build security in
to the protocols—you build it into the building! It’s easier to use locks and guards to
ensure security than fancy encryption. The easiest way to keep someone from
snooping or tampering with data on the network is simply to deny them access to
the hosts that connect to the network