DNS Blacklisting vs Active Content
The most common type of content filtering is dependent upon the effectiveness of a comprehensive blacklist. This is massive, ever-growing and changing database of known domains (www.pornsite.com), URL’s (http://www.pornsite.com/badpic.htm) or IP addresses (http://207.45.79.112) that have been collected by a “watchdog” service for specific content.
The blacklist contains hundreds of thousands of these entries, categorized in various groups – porn, gambling, drugs, social media, sports, intolerance, shopping, etc.
Most importantly, the database will also include a list of any IPs or URLs known to be malicious, suspicious or recently hacked.
When a web page is requested, if its domain, URL, or ip address match one in the blacklist, the web page is not displayed.
The Problem
Webmasters for controversial web sites know that blacklists are prevalent. To ensure access, they constantly relocate their sites. Links are then updated, and new information is submitted to search engines. As a result, even the most comprehensive, well-maintained blacklist is rendered incomplete and ineffective. It is a cat and mouse game, and the bad guys usually win.
Reading Between the Lines
Using a method of intelligent text processing, Active Content Filtering is not entirely dependent on the accuracy and “freshness” of given list or database of sites and IP addresses. Instead, the actual text of target pages are examined and interpreted in real is reviewed before any requested site is displayed to a screen.
If the system detects a series of phrases or words with questionable usage, the page is blocked. The decision to block a page is not arbitrary, however. An intelligent, customizable rule set is applied to potentially unwanted text, ensuring that approved information is always accessible.