Firewalls: Motivation

In the early days of computing, there was no outside connectivity and no World Wide Web. Networks belonging to businesses would usually implemented a closed network, which typically allowed secure access only to known parties and employees. Since no 'outsider' device was connected to such a network, there was no danger of hacking this network remotely.

"Figure 10-1: Closed Network" (page 206), Nayak, U., & Rao, U. H. (2014). The InfoSec handbook: An introduction to information security (1st ed.). APRESS.