But a proxy server can do more than just cache frequently accessed data. Because the proxy server “hears” and services requests from its clients, the clients themselves do not necessarily need any direct Internet access at all. Consequently, the proxy server became a very popular way to bridge a local network, also known as a LAN or intranet, to an external network such as the Internet — as long as one computer running the proxy server could hear both networks simultaneously.
As the availability of broadband connections has grown rapidly, so has the thirst for proxy servers. This primarily because these connections offer enough bandwidth to support several machines simultaneously. The proxy server solutions require only one of these machines to maintain a connection to the broadband service, though. This can preserve IP address space and also save enterprises money on service subscription costs.
Proxy servers can be configured to allow or deny particular types of network requests, either from the LAN to the Internet, or from the Internet to the LAN. In this way, the proxy server becomes a firewall. A firewall, as its combative name implies, is a security measure that functions much like a border guard: It inspects each piece of data that tries to pass through the boundary.
Depending on the sophistication level of the firewall, it may be configurable to make a wide variety of distinctions between different types of incoming and outgoing data. Whether this data is allowed to pass into or out of the internal network depends on certain conditions, such as the originating IP address of said data. Good firewalls also provide extensive logging capabilities because a “paper trail” of network activity is key to investigating incidents or attempted incidents.
There are stand-alone firewall products, and there are proxy servers that include firewall capabilities. As a firewall is more like a moat between servers, one could argue that a firewall in and of itself is not a “server” in the traditional sense. In theory, there is nothing intrinsically superior about a dedicated firewall product vs. a proxy server with firewall capabilities. In practice, however, the latter category is finally catching up to dedicated firewall products. WinRoutePro is an example of such a product and may represent the newest generation of proxy servers with strong firewall capabilities.