网络防火墙的功能是,加强网络之间访问控制、防止外部网络用户以非法手段通过外部网络进入内部网络。它对两个或多个网络之间传输的数据包和链接方式按照一定的安全策略对其进行检查,来决定网络之间的通信是否被允许,并监视网络运行状态。它实际上是一个独立的进程或一组紧密联系的进程,运行于路由、网关或服务器上来控制经过防火墙的网络应用服务的通信流量。其中被保护的网络称为内部网络(或私有网络),另一方则称为外部网络(或公用 The function of the network firewall is to strengthen the access control between the networks and prevent the external network users from illegally entering the internal network through the external network. It examines the data packets and links transmitted between two or more networks according to a certain security policy to determine whether the communication between the networks is allowed or not and to monitor the network operation status. It is actually a stand-alone process or a group of closely linked processes that run on a route, gateway, or server to control the amount of traffic that flows through a firewall’s web application service. The protected network is called the internal network (or private network), while the other is called the external network (or public