10.1. The Purpose of the Firewall
There are several different types of firewalls and each will be discussed in detail later in this chapter, but all serve the same purpose: to separate the public and private networks, and to prevent unwanted traffic from reaching the private network.
Firewall was originally used to describe a barrier put between connected homes and apartments to reduce noise and protect neighbors from fires in neighboring units.
To understand what this means it is important to understand the structure of a firewall. A firewall consists of at least two interfaces: public and private. The public interface, generally the Internet, is the side of the firewall to which everyone has access. The private interface is the side that ...