What is a software firewall and what does it do?

A software firewall is distinct from a hardware firewall, like those offered by LinkSys. A hardware firewall protects a network while a software firewall protects an individual computer. Despite how it may sound, this is not entirely duplicative.

A hardware firewall specifically protects against incoming connections to your network from the Internet. A software firewall takes your security to the next level by regulating the network activity on the basis of a particular application, service, user, and so forth.

With a software firewall you can prevent unauthorized applications from having any access to the internet. If your computer becomes infected with a virus, worm or trojan, it will not be able to facilitate the attacker if he wants to use your computer to host illegal content or launch attacks against other computers or networks. And this does happen. Hardware firewalls do not prevent these kinds of attacks.

There are many additional features that a software firewall can provide.


   [What About the Mac OS X Built-In Firewall]

What about the Mac OS X built-in firewall? Is it sufficient?

The Mac OS X built-in firewall protects your computer agaist incoming connections, much like a hardware firewall. You can selectively choose which services are accessible to other computers on your network and the Internet.

However, this does not protect you against outgoing connections. Applications that want to "phone home", and malicious programs that try to open a connection for the attacker to use as a tunnel, use outgoing connections.


   [Is This Security an Illusion]

In the security provided by a software firewall all an illusion?

It can be. A poorly configured firewall will do nothing to protect the security of the computer, and it also has the down-side of making the user feel more secure. A good example of a poorly configured firewall is that of "trusted applications". More on that later.

A well configured software firewall will dramatically increase the security of your computer. The initial configuration process of a software firewall can be tedious, but the end result is well worth it. Instead of trusting a specific application, only trust that application to connect to specific remote hosts. For instance, instead of letting your web browser contact any website, allow it only to contact the websites that you regularly visit. If your web browser is later the subject of a security vulnerability, it is far less likely that an attacker will be able to make use of that vulnerability on your computer.