because firewalls are usually located between a company's internal network and the internet, they often provide other services that allow computer inside the company access to the internet. the most common of these services are known as PROXY SERVICES. rather than allowing individual workstations to connect directly to the internet servers, the proxy server handles the connections and sends request and replies back and forth. using a proxy server makes your network more secured.

and example of a proxi server is squid, SQUID is the most powerful proxy server there is.

you can find more information about SQUID at www.squix-cache.org