There are very different ways to interpret the concept of the "firewall". At this point we would like to explain the meaning of firewall in this manual:
A firewall is a centrally located collection of components for monitoring data exchange between two networks. In most cases, the firewall monitors the data exchange between an internal, local area network (LAN) and an external network such as the Internet.
The firewall can consist of hardware and / or software components:
- In purely hardware systems, the firewall software often runs on a proprietary operating system.
- The firewall software can also run on a normal computer with Linux, Unix or Windows, which is dedicated to this task.
- As a third and common alternative is the firewall software that runs directly within the router connecting the LAN to the Internet.
In the following sections, we will only consider the firewall in a router.
Note: The functions "intrusion detection" and "DoS prevention" are a part a firewall in some applications. These functions are also included in our router, although they are implemented as separate modules alongside the firewall. Refer to sections Protection against break-in attempts: Intrusion detection and Protection against "Denial-of-Service" attacks for further information on this.
