Anti-Pornography Filtering
by David M. Schwartz, CEO, ImaginOn, Inc.  14 October 1998

Filter Availability
Web content filtering is a controversial, emotional topic.  Many people consider it an attack on free speech.  Others believe filtering is essential to limit the exposure of children to "adult" material.  ImaginOn takes no position with regard to the morality or politics of filtering.  Given WebZinger's emphasis on real-time presentation of graphical data, ImaginOn makes a state-of-the-art filtering system available for those people who want one.  This content filter can be selected by checking the appropriate box on the "Advanced Settings" page of the WebZinger Recorder Control Panel.

In the case of WebZinger™ for Kids, a product for use primarily by children between the ages of 4 and 11, the ImaginOn Content Filter is always enabled.  This filter is designed to screen out only commercial sex websites. Websites that are informational, medical or presenting fine arts are not explicitly blocked.  So, while a search on the word "breast" will not even start, a search on "mammography" will succeed, displaying human anatomy and the word "breast", in context.   Understanding that some parents will find this approach inadequate, ImaginOn provides an additional "open" filter, under password control.  Parents can add (and later subtract) any words or phrases to (and from) the open filter.

Filter Type and Operation
The ImaginOn Content Filter is a proprietary semantic and spatial filter primarily based on words, the relationships between those words, and their position within a website.  The filter does not depend on site ratings or lists of "bad" websites.  At one level, the filter prevents searches from starting, returning the typing cursor to the beginning of the "FIND" line of the WebZinger Recorder Screen.  At another level, the source HTML of a website is parsed when the site is fetched by WebZinger.  If a blocked word or phrase is found on the website, that site is passed over.  Additional "expert rules" beyond words and word position are also utilized by the filter to screen out possibly inappropriate sites.  ImaginOn's filter also operates on website pages before they are displayed by ImaginOn's integrated browser.  A page rejection causes the browser to remain on its present page.

Filter Design Goals and Limitations
ImaginOn's content filter is designed to eliminate 99.95% (1,999 out of 2,000) of commercial sex sites in WebZinger searches where such material is incidental.  WebZinger searches on words or phrases that have obvious double meanings, such as "foxes" or "girl toys" may reduce the effectiveness of the filter to 99.5%, (199 out of 200) or less.  In practice, this means that inappropriate images will rarely, if ever, be displayed in a WebZinger slideshow containing 15 slides.

The few images that do get through the filter and its expert rules come from websites whose content does not conform to the expectations of the filter designers.  Should ongoing testing and user feedback indicate that this is a problem of increasing magnitude, the filters will be modified accordingly.  Those revisions will automatically be installed whenever the user runs the WebZinger Updater Program and a newer version of the filter is available on ImaginOn's website.

Inevitably, some websites with images that should be downloaded are passed over, due to the bias of the filter.  The rate of such "false positives" is believed to be less than 10% of the total number of sites visited by WebZinger during any given search with the filter turned on.  For searches where the search term is a pun of a sexual nature, the false positive rate may reach 30%.  The filter design purposely errs on the conservative side.