A firewall approach provides numerous advantages to sites by helping
increase overall host security. The following section provides an
overview of the primary benefits of using a firewall.
1.4 Benefits of firewalls
A firewall provides a leveraged choke point for network security.
It allows the corporation to focus on a critically vulnerable point:
where the corporation’s information system connects to the Internet.
The firewall can control and prevent attacks from insecure network
services. A firewall can effectively monitor all traffic passing through
the system. In this manner, the firewall serves as an auditor for the
system and can alert the corporation to anomalies in the system. The
firewall can also log access and compile statistics, which can be used
to create a profile of the system.
Some firewalls, on the other hand, permit only e-mail traffic
through, thereby protecting the network against any attacks other
than attacks against the e-mail service. Other firewalls provide less
strict protection and block services that are known to be problems.
Generally, firewalls are configured to protect against unauthenti-
cated interactive logins from the outside world. This, more than
anything, helps prevent vandals from logging into machines on your
network. More elaborate firewalls block traffic from the outside to the
inside but permit users on the inside to communicate freely with the
outside. The firewall can protect against any type of network-borne
attack if you unplug it.
Firewalls are also important because they can provide a single
choke point (bottleneck) where security and audit can be imposed.
Unlike in a situation where a computer system is being attacked by
someone dialing in with a modem, the firewall can act as an effective
phone tap and tracing tool. Firewalls provide an important logging
and auditing function. Often, they provide summaries to the adminis-
trator about what kinds and amount of traffic has passed through it,
how many attempts there were to break into it, etc. The following
are the primary benefits of using a firewall:
■ Protection from vulnerable services that are running on the server
that may increase its vulnerability to attack
12 1.4 Benefits of firewalls