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What Is A Firewall?

Article (PSA-0006)
Submitted by: Billy Joe Long, Member/Manager
Company: Problem Solving Applications, LLC
Titled: What Is A Firewall?
Original release date: October 15, 2017

What Is A Firewall?

The word firewall was borrowed from firefighting and fire prevention, where the word was used to indicate a barrier used to prevent the spread of fire. In network and computer security the “firewall” serves a similar purpose by providing a barrier between “trusted” and “untrusted” networks. A “trusted” network can be described as a controlled internal network, such as your home or business network. An “untrusted” network is an outside network which you do not control, such as the Internet.

A firewall can be hardware, software, or both.

How Does A Firewall Work?

A firewall monitors incoming and outgoing traffic and allows or blocks specific traffic based on a defined set of security rules. A firewall is used to help screen out hackers, viruses, and worms that try to reach your computer over the Internet.

At their most basic, firewalls work as a filter between your network and the Internet. You can configure your firewall so it knows what you want to allow in and what you want to allow out. Everything else is blocked.

There are several different methods firewalls use to filter out information, and some are used in combination. These methods work at different layers of a network, which determines how specific the filtering options can be.

Firewalls use one or more of three methods to control traffic flowing in and out of a network:

  1. Packet filtering – Packets (small chunks of data) are analyzed against a set of filters. Packets that make it through the filters are sent to the requesting system and all others are discarded.
  2. Proxy service – Information from the Internet is retrieved by the firewall and then sent to the requesting system and vice versa.
  3. Stateful inspection – A newer method that doesn’t examine the contents of each packet but instead compares certain key parts of the packet to a database of trusted information. Information traveling from inside the firewall to the outside is monitored for specific defining characteristics, then incoming information is compared to these characteristics. If the comparison yields a reasonable match, the information is allowed through. Otherwise it is discarded.

Do I Need A Firewall?

Yes. If you are using a computer and connecting to the internet with it, then you should have an active, up-to-date, firewall. If you are using a Microsoft Operating System you have a firewall already. It is called “Windows Firewall”, and can be configured to protect your computer. In most instances, the modem/gateway/router provided by your Internet Service Provider also functions as a hardware firewall, and can be configured by utilizing the provided web access interface.

If you are unsure if you have a firewall, or whether it is configured correctly – call PSA Computer Services at (707) 506-6228 to set up an appointment to have a technician come out and make sure you do!

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