What is a Firewall? -

Welcome to our first tutorial about Firewall's, written by Alan Lloyd on behalf of WWW Security Services. Some words used in this tutorial have their meanings explained. Just click the word and a popup will open our glossary section with the meaning.

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During these tutorials we will be mainly using the free firewall provided by Zone Labs.  Zone Alarm Our recommended firewall. (and no we don't sell it or get anything for promoting it. Its just good and FREE)
  

Firewall's - The Basics
    

There is no real easy way to put this. So you will have to bare with me as we go through the way a computer connects to the internet.

When you first connect to the internet via your ISP your computer is available to send and receive information. Your computer is assigned a unique IP address. This is used much the same way as a standard postal address. It tells people where to send information to you.

But obviously we don't want to be exchanging information with anybody. This is where a Firewall can come in handy.

Firewall's split all communications into two distinct category's. Incoming and Outgoing.

Incoming

This is the most dangerous, so to speak. Information has to come in to your computer. This page for instance was sent to your computer via port 80. Port what? you say.

Your computer receives certain types of information via different ports. Normal web browsing uses port 80, checking your email uses port 110 and port 25 to send email.

You really don't need to know all the ports off by heart. In fact as there are over 65,000 you would have a job. Most legitimate programs communicate throughout the lower section, from port 1 - 1024. Though there are exceptions to every rule.

What you don't however want is to allow just anyone to connect to your computer. Without a firewall your computer could accept connections from un trusted sources and then you could be in a world of trouble.

People who want to try to exploit your computer can scan for open ports on your computer. If they find one then they can potentially exploit your computer and gain access to all your information. A good Firewall will close most open ports and good firewall's will hide (stealth) your ports totally.

Outgoing

Outgoing communication is a lot simpler than incoming. Out going communications are usually initiated by programs or services running on your computer. This gives you control over what you allow or disallow on your computer.

However there are malicious programs and scripts (commonly known as Trojans) that are spread by Email usually. Once these programs get onto your computer they can open a port and just sit quietly until a hacker makes contact. This might not be the hacker that created the trojan.

The thing to remember is that one trojan can be used by any hacker. So be warned you need to do something to protect your computer.

Again a firewall can help. A good firewall such as Zone Alarm will control outgoing communications at the same time as protecting you from incoming communications.
  

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Next What does a Firewall do?

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Firewall's - Next Steps

So now we know what the problem is we need to know what we can do about it.

• Start by determining the security of your computer system. You can run one of our port scanning utility's by clicking on 'Tools' in the menu.
    
• This will quickly tell you if you need to protect your computer system.
    
• If you find open or closed ports on your computer then you either need to install a firewall or configure the one you have.
    
• Install a Firewall. Firewall's come in all shapes and sizes. We will go into this in a bit more detail in the coming sections.
  
  
• Read What does a Firewall do? if you haven't already.

This is the first of our tutorials about Firewall's, written by Alan Lloyd on behalf of WWW Security Services. You are free to reproduce this tutorial in its entirety with this statement and links left intact.

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