Anonymous proxies are an unseen threat-a student's or employee's backdoor to malicious or productivity-sapping sites on the Internet. If your URL filtering solution relies on the old-school URL database/keyword approach, your ship is leaking and you may not see the holes.

With hundreds of new proxy sites created each day, traditional URL filtering just can't keep up, even when supplemented by standard keyword analysis. What follows is a primer on the problems, the sizable costs and time drain for IT professionals, and a discussion of an effective third-generation solution that goes far beyond the traditional strategy.