Why should I use a software firewall if I have a hardware firewall installed?Well I thinked like this when I bought my router with integrated firewall, some months ago, and after some considerations I decided to keep my software firewall also. Here are some of the reasons that is necessary to use a software firewall:
1.Hardware firewall protects from external attacks and from some types of protocols, but it does not know what applications on our computer send the data to the out world.
2.The above could make people think that if I use only safe applications then I am protected; right?
Wrong. This is the biggest mistake one can do. Since all of us use internet for comunicating and navigating to sites we cannot be sure of all the data that we receive from the outside world. If we receive a virus then in the worst cases we will lose personal documents, will have to reinstall our operating system or in rare chases say goodbye to our hard disk.
3.But what happens if we receive other type of malware programs? If we receive a troian or a worm? Those can use our computer and our connection to send themselves to other computers and infect them to, or in the worst chase steal our confidential information such as name, bank accounts, visa card numbers,etc. and send it to the person that made them. Will the hardware firewall protect us?
4.The answer is no. The hardware firewall cannot know which application sends the data to the outworld. Only knows that is being send by our computer, which the hardware firewall consider safe. And here comes the necessity of using a software firewall.
5. This last one will check which application is trying to send the data in the outworld and will warn us. Then if we consider it a safe application we can allow it to send this data; or we can block it if we consider it unsafe. That is the one use that software firewalls offer and which hardware firewalls don't; it tells us of which applications connect to the internet.
6. And this is the reason that is necessary to have. Antivirus programs will warn us and block Known threats. Software firewall will inform us also about unknown threats (that connect to the net), and let us block them before they can really harm us.

ps. I tried to explain the need of a software firewall in the simplier way I could, I hope that it will help novice users understand some of the threats that are out there.
by pandlouk