WebSense and WizGuard Proxy Server are proxy servers, although they're not what we'd call industrial-strength. SurfWatch integrates with proxy products such as Microsoft's Proxy Server, acting as an add-in filter. It is vitally important that you reconfigure existing proxy servers so they won't accept requests directly from browsers, but instead allow connections only from the relay software. This action ensures that requests only flow from the browser to the relay software to the proxy server. A potential problem with relay configuration is that the process of accepting requests from clients, examining the requests, logging them and then passing the permitted requests to the Internet takes time and computing power.
Processing overhead can significantly slow down user response.
The third approach to monitoring requires modifying the client operating system or applications. SOS Pro and NNPro are based on such client-side modifications. It's the most basic architecture used for monitoring and blocking, but it's also the least satisfactory. Rollout costs are significant, and support overhead is high. And because the monitoring and blocking system works inside client software, there is the potential for a whole range of bugs and unpredictable interactions to cause problems.