What does a web proxy add besides content filtering, where do its rules come from, and what does it need in operation?

Most web proxies can authenticate users and control access by group or role, which adds access restrictions per user group, logging and traceability. Their checks combine rules the company maintains itself with patterns bought by subscription. In operation it needs care: the rule sets must be maintained in the company's interest and wrongly blocked sites released.

* Authentication by group, logging per request, and a rule set that someone has to look after. *

The interaction view: the browser asks the proxy for a resource, the proxy queries DNS, loads the resource, checks it against the rule set and the blacklist, malware and virus services, and delivers it. The admin maintains the rule set.

In one sentence: a web proxy with content control prevents unwanted content from being downloaded into a system via HTTP(S). Like the email gateway, it needs all HTTP(S) traffic to pass through it and organisational processes for its rules and for blocked sites, a point the next case studies make painfully clear.

Go deeper:

• Internet filter (content-control software) — Wikipedia — category lists, blacklists and their side effects.