Lancom Systems LCOS 3.50 8.2 What is a Firewall?

 Chapter 8: Firewall LANCOM Reference Manual LCOS 3.50

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Firewall

that a defenceless workstation installed in the Internet will - perhaps even

accidentally - become the victim of attacks.

8.2 What is a Firewall?

The term “Firewall” is interpreted very differently. We want to define at this

point the meaning of “Firewall” within the boundaries of this reference man-

ual:

The Firewall can consist of hard and/or software components:

In pure hardware systems the Firewall software often ru ns on a proprie-

tary operating system.

The Firewall software can also run on a conventional workstation, which

is dedicated to this task under Linux, Unix or Windows.

As a third and frequently used alternative, the Firewall software runs

directly within the router, which connects the LAN to the Internet.

In the following sections we only look at the Firewall in a router.

The functions “Intrusion Detection” and “DoS protection“ are part of

the content of a Firewall in some applications. The LANCOM contains

these functions also, but they are realised as separate modules beside

the Firewall.

Further information can be found in the section ’Protection against

break-in attempts: Intrusion Detection’ →page 160 and ’Protection

against “Denial of Service” attacks’ →page1 62.

Checking data packets

How does the Firewall supervises the data traffic? The Firewall works in prin-

ciple like a door keeper for data packets: Each packet will be checked,

whether it may pass the door of the network (Firewall) in the desired direction

or not. For such a checking different criteria are used, in common language of

Firewalls called “rules” or “guidelines”. Depending on the kind of information,

A Firewall is a compilation of components, which monitors at a central place the data exchange

between two networks. Mostly the Firewall monitors the data exchange between an internal,

local network (LAN), and an external network like the Internet.