What is Firewall??

For this post I would like to write abut the security and control which is firewall.You probably know that you need firewall security.In fact, you may even already have a firewall management program in place. But what exactly is firewall security, and what does firewall management entail?

The word firewall originally referred literally to a wall, which was constructed to halt the spread of a fire. In the world of computer firewall protection, a firewall refers to a network device which blocks certain kinds of network traffic, forming a barrier between a trusted and an untrusted network. It is analogous to a physical firewall in the sense that firewall security attempts to block the spread of computer attacks.

How Does Firewall Management Work?

A firewall management program can be configured one of two basic ways:

1. A default-deny policy. The firewall administrator lists the allowed network services, and everything else is denied.
2. A default-allow policy. The firewall administrator lists network services which are not allowed, and everything else is accepted.

A default-deny approach to firewall security is by far the more secure, but due to the difficulty in configuring and managing a network in that fashion, many networks instead use the default-allow approach. Let's assume for the moment that your firewall management program utilizes a default-deny policy, and you only have certain services enabled that you want people to be able to use from the Internet. For example, you have a web server which you want the general public to be able to access. What happens next depends on what kind of firewall security you have.