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LANCOM Reference Manual LCOS 3.50 ̈ Chapter 8: Firewall
108
Firewall
which are used for creation of the rules and which are checked during the
operation of the Firewall, one distinguishes different types of Firewalls.
Above all, the aspect of the “central” positioning is very Important: Only when
the entire data traffic between “inside” and “outside” goes through the Fire-
wall, it can fulfil its task reliably under any circumstances. Each alternative
way can reduce or even turn off the security of the Firewall. This central posi-
tion of the Firewall simplifies by the way also the maintenance: One Firewall
as common passage between two networks is certainly easier to maintain
than a “Personal Firewall” on each of the workstations belonging to the LAN.
In principle, Firewalls operate at the interconnection between two or
more networks. For the following explanation, we only look as exam-
ple at the passage between a local network of a company and the
Internet. These explanations can be transferred however in a general
manner also to other network constellations, e.g. for the protection of
a subnetwork of the personnel department of a company against the
remaining network users.
Logging and alerting
An important function of the Firewall is beside the checking of data packets
and the right reaction to the results of this checking also the logging of all
actions triggered by the Firewall. By analyzing these protocols, the adminis-
trator can draw conclusions from the occurred attacks and on the basis of this
information he can, if necessary, go on to improve the configuration of the
Firewall.
But sometimes, logging alone comes too late. Often, an immediate interven-
tion of the administrator can prevent a major danger. That is why Firewalls
have mostly an alerting function, by which the Firewall notifies the adminis-
trator e.g. by e-mail.
8.2.2 Different types of Firewalls
During the last years, the operating principles of Firewalls have more and
more evolved. Under the generic term “Firewall”, a whole range of different
technical concepts is offered to protect the LAN. Here we introduce the most
important ones.