Firewalls and Internet Security - Your First Defense

Internet security is a growing concern for the average user. It seems like the Internet is full of viruses and worms - you may even have had to deal with some yourself. A computer is an important tool, an investment worth taking care of. Let's look at some basic security concepts and their importance in everyday computing.

What is a port?

Much like a harbor is a safe haven for ships, a port is a place where information can enter and leave your computer. Firewalls are the harbors that shelter these ports and allow traffic. Ports are not physical openings; they are doorways that can be opened and closed. Data from networks comes through these ports and interacts with your computer.

Why does it matter?

If every port was open on a computer, you would have no control over what information is received by your computer. It's not wise to leave your front door wide opened and unlocked, so why should you treat your computer differently? Firewalls can be configured to filter outgoing traffic as well, effectively blocking access to sites and providing a parental control over Internet access.

What's a firewall?

Your first and foremost defense from the outside world is to do the obvious: close doorways. If someone was breaking into your house, you'd close the door - and lock it too. Firewalls can do this by 'closing' ports. If a port is closed, it receives no traffic. Firewalls also filter the data coming through. You may open your door for a neighbor, but not for a someone who looks suspicious or dangerous.

What is a 'stealth' port?

When a port receives data, in can optionally send data back. This information is often useful, showing the user what service is running for that port. It's the equivalent of having 'The Smiths' printed on your door. If a port is in 'stealth' mode, it won't send any information back. The potential burglar may leave non-the-wiser. This is commonly referred to a 'filtered' port because it 'filters' traffic.

Where and How can I get a firewall?

Many programs exist to setup your firewall for you, with handy graphical interfaces that let you set limits on who you send information to (and who you receive it from). It's likely that a firewall came with your operating system, such as the popular "iptables" for Linux. Firewalls can be software on your operating system or embedded in hardware.