What is a Firewall on a computer?

I am sure we’ve all come across this term at one point or another. But really, what is a Firewall? A firewall is a software utility or hardware device that essentially acts as a filter for data entering or leaving a network or computer. You could think of a firewall as a security guard that decides who enters or exits a building. A firewall works by blocking or restricting network ports. Firewalls are commonly used to help prevent unauthorized access to both company and home networks.

Firewalls come in two basic forms;

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  • Software Firewall and
  • Hardware Firewall.

Software Firewall

The first example of this that comes to mind is Windows Firewall. This firewall software program comes included with any version of Microsoft Windows. Software Firewalls are designed to protect a computer by blocking certain programs from sending and receiving information from a local network or the Internet.

Hardware Firewalls

Hardware firewalls a little more out-of-the-way. They are built into the routers and are designed to protect all the devices connected to a network. If you are connecting to the internet through a broadband router, the router’s firewall is already protecting your device.

So How do Firewalls work?

Network traffic is comprised of packets — there are typically many of them for any given request like loading a web page. The packets contain information about where they are coming from and where they are going and of course carry information such as the request for a web page or the response. The exact format of the packets depends on the type of software that is trying to communicate, but there are prescribed formats in various protocols.

A typical firewall is software that can look at those packets read the protocols and decide if the packet will be allowed to continue to the next step on the path between the “where they are coming from” and “where they are going”.

This software could be on your computer system, it could be in your cable modem, it could be in your internet service provider’s systems, it could be on the web services’ network or the web services’ computer system. More than likely it will be on more than one of those.

Different firewall software varies in how it looks at the packets and how you can tell it about packets that you don’t want to traverse. The firewall on your computer, for example, should look at packets coming to your computer from anywhere and decide if they are following all the rules.

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If any rules are being broken then the firewall software can take action including simply not forwarding the packet.

How do Firewalls protect Businesses

  • Large corporations often have very complex firewalls in place to protect their extensive networks.
  • On the outbound side, firewalls can be configured to prevent employees from sending certain types of emails or transmitting sensitive data outside of the network.
  • On the inbound side, firewalls can be programmed to prevent access to certain websites (like social networking sites).
  • Additionally, firewalls can prevent outside computers to attack computers inside the network.
  • A company might choose to designate a single computer on the network for file sharing and all other computers could be restricted.
  • There is no limit to the variety of configurations that are possible when using firewalls.
  • Extensive configurations typically need to be handled and maintained by highly trained IT specialists, however.

The need for Firewalls for Personal Use

  • For home use, firewalls work much more simply.
  • The main goal of a is to protect your personal computer and private network from malicious mischief.
  • Malware, malicious software, is the primary threat to your home computer. Viruses are often the first type of malware that comes to mind. A virus can be transmitted to your computer through email or over the Internet and can quickly cause a lot of damage to your files. Other malware includes Trojan horse programs and spyware.
  • These malicious programs are usually designed to acquire your personal information for the purposes of identity theft of some kind.
  • There are two ways a can prevent this from happening.
  • It can allow all traffic to pass through except data that meets a predetermined set of criteria, or it can prohibit all traffic unless it meets a predetermined set of criteria.

One thing worth noting is that a firewall only acts as the first line of defense. It doesn’t provide comprehensive protection against all threats such as most viruses, spam messages, and malware. For a more comprehensive protection for your device, you should also install the latest antivirus and antimalware programs. Keeping your Operating system and other anti-malware solutions up-to-date also goes a long way in ensuring your safety when browsing the web.


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