Mastering™ Network Security, Second Edition

5.3. When Is a Firewall Required?

Traditionally, firewalls have been used to control access between the internal network of an organization and the Internet, but as network boundaries have blurred (due to the additional of wireless networks, VPN for remote clients, and extranets) and as malicious code has proliferated, firewalls are increasingly becoming a basic function that is added to every network-capable host. At a minimum, however, there are situations in which firewalls are clearly necessary.

5.3.1. Dial-In Modem Pool and Client-Initiated VPN

A firewall can be used to control access from a dial-in modem pool or a client-initiated VPN (virtual private network). For example, an organization might have an access control policy that specifies ...