In this project, we will design and implement $$multi$-$threaded application$-$layer proxy firewall$$ using the

Windows standard socket interface $($Winsock$).$ The proxy firewall is an intermediate server $($A$.$K$.$A$,$proxy$),$

which works as a middleman between clients and a server as shown in Fig. $1$ below. The example in the figure

shows an application$-$layer security firewall for a web server, but such a security firewall can be used virtually for

any client$-$server based network applications. In the figure, the proxy behaves as if it were the real web server to

clients. The client first transmits a HTTP GET request $($as a text message$)$ to the proxy, requesting a target web

page. Then, the proxy scans the contents in the GET command, looking for any possibility hazardous contents to

be removed before such hazardous contents reach the real web server. The security firewall also monitors any

hazardous contents to prevent any secure information from leaking to the outside of the web server.