A server, usually a caching Web server, that helps to implement a firewall around a closed network. It is a server which is accessible by the general public and which dispenses Web pages stored inside the closed network. Any request for a Web page from outside the closed network is checked by the Web server to ensure that it is a page that can be sent to an outside user. If the page is in the server's cache then it is sent immediately; if not, the page is retrieved from a safe Web server inside the closed network. In this way the proxy server acts as a secure front end to a vulnerable server. If a cracker wished to infiltrate the closed network, he or she would have to attack the proxy server first. A proxy Web server is often used in conjunction with a firewall router; this configuration is known as a screened host firewall. Proxy servers are also used to provide fast access to cached Web pages. See caching Web server. A proxy server does not have to implement a firewall; it could just be used to speed up access to Web pages.