Reverse proxy means that the proxy server accepts the connection request on the Internet, then forwards the request to the server on the internal network, and returns the result from the server to the client requesting the connection on the Internet. At this point, the proxy server looks like a server to the outside.

The usual proxy server is only used to proxy the connection request from the internal network to the Internet. The client must specify a proxy server and send it directly to the Web server to search for multiple uncertain servers, instead of accessing a fixed server for the requests of multiple clients on the Internet. Therefore, ordinary Web proxy servers do not support external access requests to internal networks. When the proxy server can access the internal network on behalf of the host on the external network, this proxy service mode is called reverse proxy service. At this time, the proxy server appears as a Web server, and the external network can simply regard it as a standard Web server without special configuration. The difference is that this server does not save any real data of Web pages, and all static web pages or CGI programs are saved on the internal web server. Therefore, the attack on the reverse proxy server will not destroy the Web page information, thus enhancing the security of the web server. The reverse proxy mode does not conflict with packet filtering mode or ordinary proxy mode, and can be used in firewall devices at the same time. The external network uses the reverse proxy mode when accessing the internal network, and uses the forward proxy mode or packet filtering mode to reject other external access modes, thus providing the internal network with access to the external network. Therefore, these methods can be combined to provide the best secure access.