Firewall is a term commonly used to refer to a component

Firewall is a term commonly used to refer to a component or a set of network components, which serve to restrict access between two networks, more specifically, between the internal network with a global network Internet. Firewalls have several tasks: First and foremost is: must be able to implement security policies in the network (site security policy). If certain actions are not permitted by this policy, the firewall must be assured that all the effort that represents the operation should fail or be defeated. Thus, all the illegal access between networks (not authorized) will be rejected. Perform filtering: require all existing traffic to pass through the firewall for all the process of granting and utilization of information services. In this context, the flow of data packets from / to the firewall, have been selected based on the IP-address, port number, or direction, and adapted to the security policy. Firewalls also need to record / record suspicious events and notify administrators of all the efforts through security policy. Planning Network Planning With Firewall firewall system on the network, is closely related to what kind of facilities will be provided for the users, the extent of the risk-level security that can be accepted, and how much time, money and expertise are available (technical and economic factors). Firewalls are generally composed of the filter (also called a screen or a choke) and the gateway (gate). Filter function to restrict access, narrowing the channel, or to block certain traffic classes. The occurrence of access restrictions, will reduce the function of the network. To keep the network communication function in an environment that had a firewall, generally taken two ways: First, if we imagine the network we are in a fortress of protection, communication can occur through the exit doors of the fortress. This method is known as packet-filtering, which filters only be used to deny traffic on an unused channel or canal with pretty big-security risks, while traffic on other channels are still allowed. The second method, using the proxy system, where every communication that occurs between the two networks must be made through an operator, in this case the proxy server. Some protocols, such as telnet and SMTP (Simple Mail Transport Protocol), will be more effectively dealt with the evaluation packet (packet filtering), while others such as FTP (File Transport Protocol), Archie, Gopher and HTTP (Hyper-Text Transport Protocol) will more effectively handled by a proxy system. Most firewalls use a combination of these techniques (packet filtering and proxies).