Understanding Redirect Web Filtering

With redirect Web filtering, the Web filtering module intercepts an HTTP request. The URL in the request is then sent to the external Websense server, which makes a permit or a deny decision. If access is permitted to the URL in question, the original HTTP request and all the subsequent requests are sent to the intended HTTP server. But if access is denied to the URL in question, a blocking message is sent to the client.

Note: Web filtering is performed on all the methods defined in HTTP 1.0 and HTTP 1.1. However, redirect Web filtering does not support HTTPS traffic because it cannot be decrypted to obtain the URL.

Note: Decision making from real-time options provides a higher level of accuracy, therefore caching for redirect Web filtering is not supported.

Note: Redirect Web filtering does not require a subscription license.

Redirect Web Filtering: Process Overview

This is a general description of how Web traffic is intercepted, redirected, and acted upon by the Web filtering module.

1. A Web client establishes a TCP connection with the Web server.
2. The Web client then sends an HTTP request.
3. The device intercepts the requests and extract URL. The URL is checked against Global Web filtering white and blacklists. If no match is made, the Websense server configuration parameters are utilized. Otherwise go to step 6.
4. The URL is sent to the Websense server for checking,
5. The Websense server returns a response indicating whether or not the URL is to be permitted or blocked.
6. If access is allowed, then the original HTTP request is sent to the Web server. If access is denied, the device sends a blocking message to the client and tears down the TCP connection.