So, you have now read about firewalls and how they function. Firewalls are usually dedicated machines that do nothing else, or not much else, then to filter traffic.
The problem arises then, what to do about a normal home user? normally home users have one computer per family (if not normally, there is plenty of these cases).Most of these Computers are hooked up directly via a modem or broadband connection to the internet. This means they are totally exposed and since most normal users dont know about “hardening a computer” (make it more locked for outside people” and hardening alone is nor enough generally, personal firewalls (also known as software firewalls) have been made.

These are essentially programs that you run on your computer that “sit” before your internet connection and inspect everything that comes in and goes out. Most of them will nowadays even inspect which program is trying to access the internet , for example if notepad.exe will want to access the internet its a bit strange since notepad is a simple text editor and has nothing to do on the internet. That would then most likely be a Trojan horse or a Virus. The following image kind of describes the purpose of a personal firewall.

Now you ask, well why are they necessary? And here is the simple answer: Hackers/crackers used to crack for fun and because they could. Usually they stayed away from home users since there was nothing to gain from a home machine. Well, times have changed. Nowadays hackers/crackers break into your computer to install some small programs which give them remotely full control over your computer without you knowing about it. These remote controlled computers are called Zombies. Hackers/Crackers then sell these zombies to other people, for example Spammers, who then use your computer for other purposes, in the case of spammers, sending spam mail into the world from your computer.
With the coming of broadband internet, these zombies can do much more damage then when they just had a slow modem. imagine a network of 10000 zombies (quite normal size nowadays actually), each having an average of 128kilobits/second (roughly 2 emails per second), that would give the spammer the possibility of sending up to 20000 spam emails PER SECOND. By the way, 10000 zombies is not that big of a number, there have been bigger numbers. a personal firewall would prevent most of these machine to answer much less to be hacked remotely. The other way to take over a computer is of course through a virus, but that subject i will take more detailed on in another article.

well there you have it, personal firewalls are programs that check every internet / network traffic that goes in or out of your computer. As a reference some popular personal firewall products are listed here:

• Symantec (Norton) Internet Security
• Zonelabs Zonealarm
• Blackice Defender
• Microsoft Windows Firewall (Service Pack 2)

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