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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.
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