What is a firewall? A simple explanation

Published: 11-May-2001

A firewall protects your network from unwanted Internet traffic. The primary functions of a firewall are to let good traffic pass through while ‘bad’ traffic gets blocked. The most important part of a firewall is its access control features that distinguish between good and bad traffic. 

When installed, a firewall exists between your computer(s) and the Internet. The firewall lets you request web pages, download files, chat, etc. while making sure other people on the internet can not access services on your computer like file or print sharing. Some firewalls are pieces of software that run on your computer. Other firewalls are built into hardware and protect your whole network from attacks.

Everyone connected to the Internet should be running some sort of firewall. Programs can be downloaded on the Internet that can scan huge ranges of IP address for vulnerabilities like file sharing services. These programs are easy to download and run. Almost no network knowledge is needed to use these programs to exploit or harm your computer. Any kind of firewall will keep you safe from these types of attacks.

Software firewalls are programs that run on your computer and nestle themselves between your network card software drivers and your operating system. They intercept attacks before your operating system can even acknowledge them. Many free firewalls of this type exist on the Internet. Here are some free firewalls

The firewalls that are built into broadband routers and software like Microsoft ICS are very simple firewalls. They protect your LAN by not letting anyone figure out how to ‘directly’ talk to any of the computers on your LAN. This level of protection will keep out almost all kinds of hackers. Advanced hackers may be able to take advantage of certain inadequacies of NAT based firewalls, but they are few and far between.

The new trend in home networking firewalls is called stateful packet inspection. This is an advanced form of firewall that examines each and every packet of data as it travels through the firewall. The firewall scans for problems in the packet that might be a symptom of a ‘denial of service’ (dos) attack or advanced attacks.

Most people are never subject to these types of attacks, but there are some areas of the Internet that invite these kinds of attacks. Most often, these attacks come from being involved in certain kinds of competitive on-line gaming or participating in questionable mIrc channels.

 

What is a firewall? A simple explanation