separate patrons during Internet sessions so that they will not
see what other patrons are viewing. The simplest way to achieve
this result is to position the library's public Internet
terminals so that they are located away from traffic patterns in
the library (and from other terminals), for example, by placing
them so that they face a wall. This method is obviously
constrained by libraries' space limitations and physical layout.
Some libraries have also installed privacy screens on their
public Internet terminals. These screens make a monitor appear
blank unless the viewer is looking at it head-on. Although the
Multnomah and Fort Vancouver Libraries submitted records showing
that they have received few complaints regarding patrons'
unwilling exposure to materials on the Internet, privacy screens
do not always prevent library patrons or employees from
inadvertently seeing the materials that another patron is viewing
when passing directly behind a terminal. They also have the
drawback of making it difficult for patrons to work together at a
single terminal, or for librarians to assist patrons at
terminals, because it is difficult for two people to stand side
by side and view a screen at the same time. Some library patrons
also find privacy screens to be a hindrance and have attempted to
remove them in order to improve the brightness of the screen or
to make the view better.
Another method that libraries use to prevent patrons from
seeing what other patrons are viewing on their terminals is the
installation of "recessed monitors." Recessed monitors are
computer screens that sit below the level of a desk top and are
viewed from above. Although recessed monitors, especially when
combined with privacy screens, eliminate almost all of the
possibility of a patron accidentally viewing the contents on
another patron's screen, they suffer from the same drawbacks as
privacy screens, that is, they make it difficult for patrons to
work together or with a librarian at a single terminal. Some
librarians also testified that recessed monitors are costly, but
did not indicate how expensive they are compared to privacy
screens or filtering software. A related technique that some
public libraries use is to create a separate children's Internet
viewing area, where no adults except those accompanying children
in their care may use the Internet terminals. This serves the
objective of keeping children from inadvertently viewing
materials appropriate only for adults that adults may be viewing
on nearby terminals.
A third set of techniques that public libraries have used to
enforce their Internet use policies takes the opposite tack from
the privacy screens/recessed monitors approach by placing all of
the library's public Internet terminals in prominent and visible
locations, such as near the library's reference desk. This
approach allows librarians to enforce their library's Internet
use policy by observing what patrons are viewing and employing
the tap-on-the-shoulder policy. Under this approach, when
patrons are viewing materials that are inconsistent with the
library's policies, a library staff member approaches them and
asks them to view something else, or may ask them to end their
Internet session. A patron who does not comply with these
requests, or who repeatedly views materials not permitted under
the library's Internet use policy, may have his or her Internet
or library privileges suspended or revoked. But many librarians
are uncomfortable with approaching patrons who are viewing
sexually explicit images, finding confrontation unpleasant.
Hence some libraries are reluctant to apply the tap-on-the-
shoulder policy.
The fourth category of methods that public libraries employ
to enforce their Internet use policies, and the one that gives
rise to this case, is the use of Internet filtering software.
According to the June 2000 Survey of Internet Access Management
in Public Libraries, approximately 7% of libraries with public
Internet access had mandated the use of blocking programs by
adult patrons. Some public libraries provide patrons with the
option of using a blocking program, allowing patrons to decide
whether to engage the program when they or their children access
the Internet. Other public libraries require their child patrons
to use filtering software, but not their adult patrons.
Filtering software vendors sell their products on a
subscription basis. The cost of a subscription varies with the
number of computers on which the filtering software will be used.
In 2001, the cost of the Cyber Patrol filtering software was
$1,950 for 100 terminal licenses. The Greenville County Library
System pays $2,500 per year for the N2H2 filtering software, and
a subscription to the Websense filter costs Westerville Public
Library approximately $1,200 per year.
No evidence was presented on the cost of privacy screens,
recessed monitors, and the tap-on-the-shoulder policy, relative
to the costs of filtering software. Nor did any of the libraries
proffered by the government present any quantitative evidence on
the relative effectiveness of use of privacy screens to prevent
patrons from being unwillingly exposed to sexually explicit
material, and the use of filters, discussed below. No evidence
was presented, for example, comparing the number of patron
complaints in those libraries that have tried both methods.
The librarians who testified at trial whose libraries use
Internet filtering software all provide methods by which their
patrons may ask the library to unblock specific Web sites or
pages. Of these, only the Tacoma Public Library allows patrons
to request that a URL be unblocked without providing any
identifying information; Tacoma allows patrons to request a URL
by sending an email from the Internet terminal that the patron is
using that does not contain a return email address for the user.
David Biek, the head librarian at the Tacoma Library's main
branch, testified at trial that the library keeps records that
would enable it to know which patrons made unblocking requests,
but does not use that information to connect users with their
requests. Biek also testified that he periodically scans the
library's Internet use logs to search for: (1) URLs that were
erroneously blocked, so that he may unblock them; or (2) URLs
that should have been blocked, but were not, in order to add them
to a blocked category list. In the course of scanning the use
logs, Biek has also found what looked like attempts to access
child pornography. In two cases, he communicated his findings to
law enforcement and turned over the logs in response to a
subpoena.
At all events, it takes time for librarians to make
decisions about whether to honor patrons' requests to unblock Web
pages. In the libraries proffered by the defendants, unblocking
decisions sometimes take between 24 hours and a week. Moreover,
none of these libraries allows unrestricted access to the
Internet pending a determination of the validity of a Web site
blocked by the blocking programs. A few of the defendants'
proffered libraries represented that individual librarians would
have the discretion to allow a patron to have full Internet
access on a staff computer upon request, but none claimed that
allowing such access was mandatory, and patron access is
supervised in every instance. None of these libraries makes
differential unblocking decisions based on the patrons' age.
Unblocking decisions are usually made identically for adults and
minors. Unblocking decisions even for adults are usually based
on suitability of the Web site for minors.
It is apparent that many patrons are reluctant or unwilling
to ask librarians to unblock Web pages or sites that contain only
materials that might be deemed personal or embarrassing, even if
they are not sexually explicit or pornographic. We credit the
testimony of Emmalyn Rood, discussed above, that she would have
been unwilling as a young teen to ask a librarian to disable
filtering software so that she could view materials concerning
gay and lesbian issues. We also credit the testimony of Mark
Brown, who stated that he would have been too embarrassed to ask
a librarian to disable filtering software if it had impeded his
ability to research treatments and cosmetic surgery options for
his mother when she was diagnosed with breast cancer.
The pattern of patron requests to unblock specific URLs in
the various libraries involved in this case also confirms our
finding that patrons are largely unwilling to make unblocking
requests unless they are permitted to do so anonymously. For
example, the Fulton County Library receives only about 6
unblocking requests each year, the Greenville Public Library has
received only 28 unblocking requests since August 21, 2000, and
the Westerville, Ohio Library has received fewer than 10
unblocking requests since 1999. In light of the fact that a
substantial amount of overblocking occurs in these very
libraries, see infra Subsection II.E.4, we find that the lack of
unblocking requests in these libraries does not reflect the
effectiveness of the filters, but rather reflects patrons'
reluctance to ask librarians to unblock sites.
5. Internet Filtering Technology
1. What Is Filtering Software, Who Makes It, and
What Does It Do?
Commercially available products that can be configured to
block or filter access to 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 which they have created unique
definitions. SurfControl uses 40 such categories, N2H2 uses 35
categories (and seven "exception" categories), Websense uses 30
categories, and Secure Computing uses 30 categories. Filtering
software customers choose which categories of URLs they wish to
enable. A user "enables" a category in a filtering program by
configuring the program to block all of the Web pages listed in
that category.
The following is a list of the categories offered by each of
these four filtering programs. SurfControl's Cyber Patrol offers
the following categories: Adult/Sexually Explicit;
Advertisements; Arts & Entertainment; Chat; Computing & Internet;
Criminal Skills; Drugs, Alcohol & Tobacco; Education; Finance &
Investment; Food & Drink; Gambling; Games; Glamour & Intimate
Apparel; Government & Politics; Hacking; Hate Speech; Health &
Medicine; Hobbies & Recreation; Hosting Sites; Job Search &
Career Development; Kids' Sites; Lifestyle & Culture; Motor
Vehicles; News; Personals & Dating; Photo Searches; Real Estate;
Reference; Religion; Remote Proxies; Sex Education; Search
Engines; Shopping; Sports; Streaming Media; Travel; Usenet News;
Violence; Weapons; and Web-based Email.
N2H2 offers the following categories: Adults Only; Alcohol;
Auction; Chat; Drugs; Electronic Commerce; Employment Search;
Free Mail; Free Pages; Gambling; Games; Hate/Discrimination;
Illegal; Jokes; Lingerie; Message/Bulletin Boards;
Murder/Suicide; News; Nudity; Personal Information; Personals;
Pornography; Profanity; Recreation/Entertainment; School Cheating
Information; Search Engines; Search Terms; Sex; Sports; Stocks;
Swimsuits; Tasteless/Gross; Tobacco; Violence; and Weapons. The
"Nudity" category purports to block only "non-pornographic"
images. The "Sex" category is intended to block only those
depictions of sexual activity that are not intended to arouse.
The "Tasteless/Gross" category includes contents such as
"tasteless humor" and "graphic medical or accident scene photos."
Additionally, N2H2 offers seven "exception categories." These
exception categories include Education, Filtered Search Engine,
For Kids, History, Medical, Moderated, and Text/Spoken Only.
When an exception category is enabled, access to any Web site or
page via a URL associated with both a category and an exception,
for example, both "Sex" and "Education," will be allowed, even if
the customer has enabled the product to otherwise block the
category "Sex." As of November 15, 2001, of those Web sites
categorized by N2H2 as "Sex," 3.6% were also categorized as
"Education," 2.9% as "Medical," and 1.6% as "History."
Websense offers the following categories: Abortion Advocacy;
Advocacy Groups; Adult Material; Business & Economy; Drugs;
Education; Entertainment; Gambling; Games; Government; Health;
Illegal/Questionable; Information Technology; Internet
Communication; Job Search; Militancy/Extremist; News & Media;
Productivity Management; Bandwidth Management; Racism/Hate;
Religion; Shopping; Society & Lifestyle; Special Events; Sports;
Tasteless; Travel; Vehicles; Violence; and Weapons. The "Adult"
category includes "full or partial nudity of individuals," as
well as sites offering "light adult humor and literature" and
"[s]exually explicit language." The "Sexuality/Pornography"
category includes, inter alia, "hard-core adult humor and
literature" and "[s]exually explicit language." The "Tasteless"
category includes "hard-to-stomach sites, including offensive,
worthless or useless sites, grotesque or lurid depictions of
bodily harm." The "Hacking" category blocks "sites providing
information on or promoting illegal or questionable access to or
use of communications equipment and/or software."
SmartFilter offers the following categories:
Anonymizers/Translators; Art & Culture; Chat; Criminal Skills;
Cults/Occult; Dating; Drugs; Entertainment;
Extreme/Obscene/Violence; Gambling; Games; General News; Hate
Speech; Humor; Investing; Job Search; Lifestyle; Mature; MP3
Sites; Nudity; On-line Sales; Personal Pages; Politics, Opinion &
Religion; Portal Sites; Self-Help/Health; Sex; Sports; Travel;
Usenet News; and Webmail.
Most importantly, no category definition used by filtering
software companies is identical to CIPA's definitions of visual
depictions that are obscene, child pornography, or harmful to
minors. And category definitions and categorization decisions
are made without reference to local community standards.
Moreover, there is no judicial involvement in the creation of
filtering software companies' category definitions and no
judicial determination is made before these companies categorize
a Web page or site.
Each filtering software company associates each URL in its
control list with a "tag" or other identifier that indicates the
company's evaluation of whether the content or features of the
Web site or page accessed via that URL meets one or more of its
category definitions. If a user attempts to access a Web site or
page that is blocked by the filter, the user is immediately
presented with a screen that indicates that a block has occurred
as a result of the operation of the filtering software. These
"denial screens" appear only at the point that a user attempts to
access a site or page in an enabled category.
All four of the filtering programs on which evidence was
presented allow users to customize the category lists that exist
on their own PCs or servers by adding or removing specific URLs.
For example, if a public librarian charged with administering a
library's Internet terminals comes across a Web site that he or
she finds objectionable that is not blocked by the filtering
program that his or her library is using, then the librarian may
add that URL to a category list that exists only on the library's
network, and it would thereafter be blocked under that category.
Similarly, a customer may remove individual URLs from category
lists. Importantly, however, no one but the filtering companies
has access to the complete list of URLs in any category. The
actual URLs or IP addresses of the Web sites or pages contained
in filtering software vendors' category lists are considered to
be proprietary information, and are unavailable for review by
customers or the general public, including the proprietors of Web
sites that are blocked by filtering software.
Filtering software companies do not generally notify the
proprietors of Web sites when they block their sites. The only
way to discover which URLs are blocked and which are not blocked
by any particular filtering company is by testing individual URLs
with filtering software, or by entering URLs one by one into the
"URL checker" that most filtering software companies provide on
their Web sites. Filtering software companies will entertain
requests for recategorization from proprietors of Web sites that
discover their sites are blocked. Because new pages are
constantly being added to the Web, filtering companies provide
their customers with periodic updates of category lists. Once a
particular Web page or site is categorized, however, filtering
companies generally do not re-review the contents of that page or
site unless they receive a request to do so, even though the
content on individual Web pages and sites changes frequently.
2. The Methods that Filtering Companies Use to
Compile Category Lists
While the way in which filtering programs operate is
conceptually straightforward by comparing a requested URL to a
previously compiled list of URLs and blocking access to the
content at that URL if it appears on the list accurately
compiling and categorizing URLs to form the category lists is a
more complex process that is impossible to conduct with any high
degree of accuracy. The specific methods that filtering software
companies use to compile and categorize control lists are, like
the lists themselves, proprietary information. We will therefore
set forth only general information on the various types of
methods that all filtering companies deposed in this case use,
and the sources of error that are at once inherent in those
methods and unavoidable given the current architecture of the
Internet and the current state of the art in automated
classification systems. We base our understanding of these
methods largely on the detailed testimony and expert report of
Dr. Geoffrey Nunberg, which we credit. The plaintiffs offered,
and the Court qualified, Nunberg as an expert witness on
automated classification systems.
When compiling and categorizing URLs for their category
lists, filtering software companies go through two distinct
phases. First, they must collect or "harvest" the relevant URLs
from the vast number of sites that exist on the Web. Second,
they must sort through the URLs they have collected to determine
under which of the company's self-defined categories (if any),
they should be classified. These tasks necessarily result in a
tradeoff between overblocking (i.e., the blocking of content that
does not meet the category definitions established by CIPA or by
the filtering software companies), and underblocking (i.e.,
leaving off of a control list a URL that contains content that
would meet the category definitions defined by CIPA or the
filtering software companies).
1. The "Harvesting" Phase
Filtering software companies, given their limited resources,
do not attempt to index or classify all of the billions of pages
that exist on the Web. Instead, the set of pages that they
attempt to examine and classify is restricted to a small portion
of the Web. The companies use a variety of automated and manual
methods to identify a universe of Web sites and pages to
"harvest" for classification. These methods include: entering
certain key words into search engines; following links from a
variety of online directories (e.g., generalized directories like
Yahoo or various specialized directories, such as those that
provide links to sexually explicit content); reviewing lists of
newly-registered domain names; buying or licensing lists of URLs
from third parties; "mining" access logs maintained by their
customers; and reviewing other submissions from customers and the
public. The goal of each of these methods is to identify as many
URLs as possible that are likely to contain content that falls
within the filtering companies' category definitions.
The first method, entering certain keywords into commercial
search engines, suffers from several limitations. First, the Web
pages that may be "harvested" through this method are limited to
those pages that search engines have already identified.
However, as noted above, a substantial portion of the Web is not
even theoretically indexable (because it is not linked to by any
previously known page), and only approximately 50% of the pages
that are theoretically indexable have actually been indexed by
search engines. We are satisfied that the remainder of the
indexable Web, and the vast "Deep Web," which cannot currently be
indexed, includes materials that meet CIPA's categories of visual
depictions that are obscene, child pornography, and harmful to
minors. These portions of the Web cannot presently be harvested
through the methods that filtering software companies use (except
through reporting by customers or by observing users' log files),
because they are not linked to other known pages. A user can,
however, gain access to a Web site in the unindexed Web or the
Deep Web if the Web site's proprietor or some other third party
informs the user of the site's URL. Some Web sites, for example,
send out mass email advertisements containing the site's URL, the
spamming process we have described above.
Second, the search engines that software companies use for
harvesting are able to search text only, not images. This is of
critical importance, because CIPA, by its own terms, covers only
"visual depictions." 20 U.S.C. Sec. 9134(f)(1)(A)(i); 47 U.S.C. Sec.
254(h)(5)(B)(i). Image recognition technology is immature,
ineffective, and unlikely to improve substantially in the near
future. None of the filtering software companies deposed in this
case employs image recognition technology when harvesting or
categorizing URLs. Due to the reliance on automated text
analysis and the absence of image recognition technology, a Web
page with sexually explicit images and no text cannot be
harvested using a search engine. This problem is complicated by
the fact that Web site publishers may use image files rather than
text to represent words, i.e., they may use a file that computers
understand to be a picture, like a photograph of a printed word,
rather than regular text, making automated review of their
textual content impossible. For example, if the Playboy Web site
displays its name using a logo rather than regular text, a search
engine would not see or recognize the Playboy name in that logo.