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A firewall protects your local area
network (LAN) — or even a single
computer — against outside
intrusion. Firewalls work as filters
between the outside world and
private networks, approving some
types of traffic (such as when
someone accesses a Web page) and
blocking others (when unauthorized
users attempt to access your
network).
The term "firewall" doesn't actually
refer to any one device. A firewall
could be either a piece of hardware
or software, and more than one type
of firewall can be used to provide
extra network security.
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There are two common types of
firewalls:
Packet-filtering firewalls.
These firewalls apply
predefined rules to filter the
chunks of data, or packets, that
pass through it. The filter accepts
or rejects packets based on the
originating computer's network
address or other characteristics.
The packet filter might be a
computer or part of a separate piece
of hardware, such as a router.
Proxy servers
Also known as gateways, a
proxy server acts as a middleman
that relays data between a network
and the outside world. The proxy
prevents outsiders from gathering
information about computers inside a
network. The proxy can also screen
packets based on their application
type (Web access or email, for
example) or other identifying
traits.
A firewall can also screen internal
traffic on a network, separating
different departments or branches of
a large company. In some cases, a
business will configure a proxy
server to block employee access to
certain types of Internet content,
such as streaming audio or video. |
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Security Issues When Connecting to the Internet
When you connect your private network to the
Internet, you are physically connecting your network
to well over 50,000 unknown networks and all of
their users. While such connections open the door to
many useful applications and provide great
opportunities for information sharing, most private
networks contain some information that should not be
shared with outside users on the Internet. In
addition, not all Internet users are involved in
lawful activities. These two statements foreshadow
the key questions behind most security issues on the
Internet:
How do you protect confidential information from
those who do not explicitly need to access it?
How do you protect your network and its resources
from malicious users and accidents that originate
outside of your network? |
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