My employer, the San Jose Public Library, has recently been putting a lot of time and effort in to researching internet filters in response to a city council member’s proposal that the city implement mandatory filters on all of the library’s public access computers. You can read about our process, documentation, and so forth on our public webpage about the issue (linked from our homepage).
We presented the issue to the Library Commission at their last meeting, which recommended that the library not install filters, but instead continue its practice of providing privacy screens. The issue now goes to the City Council in March.
The venerable Mary Minow attended to speak out against filters from a legal standpoint. She blogged about her experience at the meeting. She also linked to the report on internet filtering that I wrote, examining the functionality of three internet filtering products: WebSense Enterprise, CyberPatrol, and FilterGate.
The average results from all three filters were telling. The accuracy rates for the filtering of keyword searching and direct URL access to sites were on par with previous studies – approximately 85% of "trigger sites" are blocked correctly, and approximately 85% of "non-trigger sites" are allowed through correctly — leaving a 15% error rate in either direction. The accuracy for images (38%) and image email attachments (25%) were much lower. RSS feeds barely passed the halfway mark, at 53% accurate. Catalog searches fared better at 67% and database searches better yet, at 83%. Here’s a table to make the data easier to read. Conclusions? Traditional text content is handled at around 85% effectiveness, but non-traditional text content, and non-text content like images, are not handled at nearly the same levels.
Average Filter Accuracy (margin of error +/- 5%)
|Type of content tested||Accuracy Percentage|
|Content of an Adult Sexual Nature – direct URL access||89%|
|Content of an Adult Sexual Nature – keyword searches||83%|
|Content not of an Adult Sexual Nature – direct URL access||88%|
|Content not of an Adult Sexual Nature – keyword searches||62%|
|Library Catalog Searches||67%|
|Library Database Searches||83%|
We do hope to write something formal up for the library community about this experience. Stay tuned!