Internet Firewall: The Basics
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Firewall. In today's high tech world where business and home computers alike are interconnected in one huge web, this word offers comfort that somehow, your computer is protected from the many threats besieging it. Many experts advocate setting up a firewall on a computer as the first step in online security. But what exactly is a firewall?
A firewall is a piece of software or hardware that prevents some communications forbidden by security policy in a computer network environment. Quite a convoluted definition? Here's a simple one: a firewall basically keeps information from leaking out (vital to businesses with huge amounts of confidential information online) and leaking in (who wants viruses and worms in their PCs?).
According to Andrew Tanenbaum (Computer Networks, Fourth Edition), firewalls are "a modern adaptation of that old medieval security standby: digging a deep moat around your castle". It’s a simple but precise analogy. Firewalls control the traffic between two "zones of trust" by forcing everyone to enter or leave through a single point of access (which Tanenbaum describes as an "electronic drawbridge"). Usually, these zones of trust involve the Internet and an internal network (e.g. a company intranet).
It's good, but not vital, to know that Internet firewalls get their moniker from the firewalls used in construction. These firewalls are simply fire-resistant wall assemblies.
Firewalls can be for personal use (single computer) or network use (placed on the boundary of two or more networks). As mentioned, firewalls can be pieces of software or hardware.
Various firewall configurations exist, though one example boasting of great security involves two components: two routers and an application gateway. Simpler configurations can’t match the security of a two-component firewall as the latter has more than one security checkpoint to pass through.
Firewalls shield a single computer
or a network from many threats, but there are adversaries that cannot
simply be defeated by firewalls. Read more on our article on Internet
security threats.
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