certain material on the Internet are among the  technology protection measures  that may

be used to attempt to comply with CIPA.  There are numerous filtering software products

available commercially.  Three network based filtering products   SurfControl's Cyber

Patrol, N2H2's Bess/i2100, and Secure Computing's SmartFilter   currently have the

lion's share of the public library market.  The parties in this case deposed representatives

from these three companies.  Websense, another network based blocking product, is also

currently used in the public library market, and was discussed at trial.  

Filtering software may be installed either on an individual computer or on a

computer network.  Network based filtering software products are designed for use on a

network of computers and funnel requests for Internet content through a centralized

network device.   Of the various commercially available blocking products, network 

based products are the ones generally marketed to institutions, such as public libraries,

that provide Internet access through multiple terminals. 

Filtering programs function in a fairly simple way.  When an Internet user requests

access to a certain Web site or page, either by entering a domain name or IP address into

a Web browser, or by clicking on a link, the filtering software checks that domain name

or IP address against a previously compiled  control list  that may contain up to hundreds

of thousands of URLs.  The three companies deposed in this case have control lists

containing between 200,000 and 600,000 URLs.  These lists determine which URLs will

be blocked.  

Filtering software companies divide their control lists into multiple categories for

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