If a proxy server is being used to divide up an internet connection across a network, there are many ways to configure proxy to improve the security and policy enforcement needs of a corporate network. In the layouts I have seen, the network engineers have chosen to configure proxy to act as a traffic monitor that essentially combs the data that passes through the proxy server to clean it of certain types of data. Virus definitions can be used to recognize an infection attempting to pass into the network and onto a client computer. This data can then be cut off before it is able to infect a system. This is a key benefit to a proxy server in general, the control and adjustment of data being transmitted inside the network.
Another popular way to configure proxy is with activity monitors that log the sites being accessed and tie those log entries to the source computer. This allows tracking of both duration of internet use and the nature of the sites being visited by users. The IP address and the machine name of the browser can be recorded to the log to allow action to be taken should it be deemed necessary based on the frequency and types of sites being visited by the end user.
To configure proxy, you have to make the determination of what rules are to be enforced. This is generally handled by management, as these are policy based choices that are based on the policies of the company that owns the proxy server. The choices made to configure proxy are then implemented by an engineer that is familiar with how to configure proxy on the server type being employed. There are many options for proxy server software, and each presents the choices to configure proxy in a different way. An engineer well versed in the software being used will be needed to configure proxy.