A firewall is a hardware or a permanent filter that monitors and data transmissions made between your PC and Internet or local network, to implement a policy filter. In computer networks, a firewall is a device or set of devices configured so as to filter, to encrypt or to arrange traffic between different security domains based on predefined rules. To protect network resources from other users of other similar networks, all consistent by links or WAN and Internet. Potential attackers are identified, their attacks on your PC or local network may be terminated.
A firewall closely cooperates with a routing program, examines each data packet is the network that will exceed through the gateway server to decide whether it will be sent on to destination or not. It also contains a firewall or proxy server works with a package that makes some needs on behalf of terminal users. The most common protective cases these programs are installed on computers that meet only the feature and is installed in the routers.