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The Effectiveness of Internet Content Filters - July 13, 2012

It is our pleasure to host this distinguished lecture by  Prof. Philip B Stark, University of California, Berkeley. The lecture will be followed by a reception. Please feel free to forward this invitation.

Date: July 13, 2012
 Time: 16:30
 Venue: Salle Paul Feidert

Abstract: As part of its defense of the Child Online Protection Act, which seeks to prevent minors from viewing commercially published harmful-to-minors material on the World Wide Web, the U.S. Department of Justice commissioned a study of the prevalence of “adult” materials and the effectiveness of Internet content filters in blocking them. As of 2005–2006, about 1.1% of webpages indexed by Google and MSN were adult—hundreds of millions of pages. About 6% of a set of 1.3 billion searches executed on AOL, MSN and Yahoo! in summer 2005 retrieved at least one adult webpage among the first ten results, and about 1.7% of those results are adult webpages. These estimates are based on both simple random samples of webpages indexed by search engines and on a stratified random sample of searches. Webpages with sexually explicit content intended for adult entertainment (i.e., not in an educational, medical or artistic context) were used to test a variety of Internet content filters for underblocking—failing to block webpages that they are intended to block. A random sample of “clean” webpages with no sexual content or reference to sex was used to test the filters for overblocking—blocking webpages they are not intended to block. Webpages retrieved by the most popular searches according to Wordtracker were also categorized and used to test filters. Generally, filters with lower rates of underblocking had higher rates of overblocking. If the filter most effective at blocking adult materials were applied to search indexes, typical query results, or the results of popular queries, the number of clean pages blocked in error would exceed the number of adult pages blocked correctly. I will discuss considerations that led to the design of the study, some of the legal hurdles in getting the data, the methods used to obtain statistically rigorous confidence intervals using the data, some of the arguments and data presented by the plaintiffs, and (time permitting) examples of spectacularly inaccurate media coverage of the litigation.

Philip B. Stark is professor and Chair of the Department of Statistics and faculty in the Graduate Program in Computational Science and Engineering at the University of California, Berkeley.  He works on uncertainty quantification and risk, with applications that include Applications include the Big Bang, causal inference, climate modeling, the U.S. census, earthquake prediction, election auditing, food web models, the geomagnetic field, geriatric hearing loss, information retrieval, risk assessment, the seismic structure of Sun and Earth, spectroscopy, and spectrum estimation.  In addition to his academic work, he has consulted for public utilities and major corporations, and a variety of state and federal agencies, including the U.S. Department of Justice, the Federal Trade Commission, the U.S. Department of Agriculture, the U.S. Department of Housing and Urban Development, the U.S. Census Bureau, the U.S. Department of Veterans Affairs, the California Secretary of State, and the Colorado Secretary of State.  Consulting topics have included truth in advertising, election contests, equal protection under the law, intellectual property and patent litigation, jury selection, trade secret litigation, employment discrimination litigation, import restrictions, insurance litigation, natural resource legislation, environmental litigation, sampling in litigation, wage and hour class actions, product liability class actions, consumer class actions, clinical trials, signal processing, geochemistry, quality control, behavioral targeting, water treatment, sampling the web, risk assessment, credit risk models, and oil exploration.  In 2000--2006, Stark conducted research for the U.S. Department of Justice in litigation over the Child Online Protection Act (COPA) and testified at trial.  He also served as a non-testifying expert in litigation over the Children's Internet Protection Act (CIPA).  Stark will discuss the research he conducted to measure how effectively Internet content filters block commercial pornography, and the extent to which they inadvertently block "clean" material.