AnInternet filter is a type ofinternet censorship that restricts or controls the content an Internet user is capable to access, especially when utilized to restrict material delivered over theInternet via theWeb,Email, or other means. Such restrictions can be applied at various levels: a government can attempt to apply them nationwide (seeInternet censorship), or they can, for example, be applied by anInternet service provider to its clients, by an employer to its personnel,by a school to its students, by a library to its visitors, by a parent to a child's computer, or by an individual user to their own computers. The motive is often to prevent access to content which the computer's owner(s) or other authorities may consider objectionable. When imposed without the consent of the user, content control can be characterised as a form of internet censorship. Some filter software includes time control functions that empowers parents to set the amount of time that child may spend accessing the Internet or playing games or other computer activities.
The term "content control" is used on occasion byCNN,[1]Playboy magazine,[2] theSan Francisco Chronicle,[3] andThe New York Times.[4] However, several other terms, including "content filtering software", "web content filter", "filtering proxy servers", "secure web gateways", "censorware", "content security and control", "web filtering software", "content-censoring software", and "content-blocking software", are often used. "Nannyware" has also been used in both product marketing and by the media. Industry research companyGartner uses"secure web gateway" (SWG) to describe the market segment.[5]
Companies that make products that selectivelyblock Web sites do not refer to these products as censorware, and prefer terms such as "Internet filter" or "URL Filter"; in the specialized case of software specifically designed to allow parents to monitor and restrict the access of their children, "parental control software" is also used. Some products log all sites that a user accesses and rates them based on content type for reporting to an "accountability partner" of the person's choosing, and the termaccountability software is used. Internet filters, parental control software, and/or accountability software may also be combined into one product.
Those critical of such software, however, use the term "censorware" freely: consider the Censorware Project, for example.[6] The use of the term "censorware" in editorials criticizing makers of such software is widespread and covers many different varieties and applications:Xeni Jardin used the term in a 9 March 2006 editorial inThe New York Times, when discussing the use of American-made filtering software to suppress content in China; in the same month a high school student used the term to discuss the deployment of such software in his school district.[7][8]
In general, outside of editorial pages as described above, traditional newspapers do not use the term "censorware" in their reporting, preferring instead to use less overtly controversial terms such as "content filter", "content control", or "web filtering";The New York Times andThe Wall Street Journal both appear to follow this practice. On the other hand, Web-based newspapers such asCNET use the term in both editorial and journalistic contexts, for example "Windows Live to Get Censorware."[9]
Filters can be implemented in many different ways: by software on a personal computer, via network infrastructure such asproxy servers,DNS servers, orfirewalls that provide Internet access. No solution provides complete coverage, so most companies deploy a mix of technologies to achieve the proper content control in line with their policies.
The Internet does not intrinsically provide content blocking, and therefore there is much content on the Internet that is considered unsuitable for children, given that much content is given certifications as suitable for adults only, e.g. 18-rated games and movies.
Internet service providers (ISPs) that block material containingpornography, or controversial religious, political, or news-related content en route are often utilized by parents who do not permit their children to access content not conforming totheir personal beliefs. Content filtering software can, however, also be used to blockmalware and other content that is or contains hostile, intrusive, or annoying material includingadware,spam,computer viruses,worms,trojan horses, andspyware.
Most content control software is marketed to organizations or parents. It is, however, also marketed on occasion to facilitate self-censorship, for example by people struggling with addictions toonline pornography, gambling, chat rooms, etc. Self-censorship software may also be utilised by some in order to avoid viewing content they consider immoral, inappropriate, or simply distracting. A number ofaccountability software products are marketed asself-censorship oraccountability software. These are often promoted by religious media and atreligious gatherings.[17]
Content filtering technology exists in two major forms:application gateway orpacket inspection. For HTTP access the application gateway is called aweb-proxy or just a proxy. Such web-proxies can inspect both the initial request and the returned web page using arbitrarily complex rules and will not return any part of the page to the requester until a decision is made. In addition they can make substitutions in whole or for any part of the returned result. Packet inspection filters do not initially interfere with the connection to the server but inspect the data in the connection as it goes past, at some point the filter may decide that the connection is to be filtered and it will then disconnect it by injecting a TCP-Reset or similar faked packet. The two techniques can be used together with the packet filter monitoring a link until it sees an HTTP connection starting to an IP address that has content that needs filtering. The packet filter then redirects the connection to the web-proxy which can perform detailed filtering on the website without having to pass through all unfiltered connections. This combination isquite popular because it can significantly reduce the cost of the system.
There are constraints to IP level packet-filtering, as it may result in rendering all web content associated with a particular IP address inaccessible. This may result in the unintentional blocking of legitimate sites that share the same IP address or domain. For instance, university websites commonly employ multiple domains under oneIP address. Moreover, IP level packet-filtering can be surpassed by using a distinct IP address for certain content while still being linked to the same domain or server.[18]
Gateway-based content control software may be more difficult to bypass than desktop software as the user does not have physical access to the filtering device. However, many of the techniques in theBypassing filters section still work.
Content labeling may be considered another form of content-control software. In 1994, theInternet Content Rating Association (ICRA) — now part of theFamily Online Safety Institute — developed a content rating system for online content providers. Using an online questionnaire a webmaster describes the nature of their web content. A small file is generated that contains a condensed, computer readable digest of this description that can then be used by content filtering software to block or allow that site.
ICRA labels come in a variety of formats.[19] These include the World Wide Web Consortium'sResource Description Framework (RDF) as well asPlatform for Internet Content Selection (PICS) labels used byMicrosoft'sInternet Explorer Content Advisor.[20]
ICRA labels are an example of self-labeling. Similarly, in 2006 theAssociation of Sites Advocating Child Protection (ASACP) initiated the Restricted to Adults self-labeling initiative. ASACP members were concerned that various forms of legislation being proposed in theUnited States were going to have the effect of forcing adult companies to label their content.[21] The RTA label, unlike ICRA labels, does not require a webmaster to fill out a questionnaire or sign up to use. Like ICRA the RTA label is free. Both labels are recognized by awide variety of content-control software.
TheVoluntary Content Rating (VCR) system was devised bySolid Oak Software for theirCYBERsitter filtering software, as an alternative to the PICS system, which some critics deemed too complex. It employsHTMLmetadata tags embedded within web page documents to specify the type of content contained in the document. Only two levels are specified,mature andadult, making the specification extremely simple.
The Australian Internet Safety Advisory Body has information about "practical advice on Internet safety, parental control and filters for the protection of children, students and families" that also includes public libraries.[22]
NetAlert, the software made available free of charge by the Australian government, was allegedly cracked by a 16-year-old student, Tom Wood, less than a week after its release in August 2007. Wood supposedly bypassed the $84 million filter in about half an hour to highlight problems with the government's approach to Internet content filtering.[23]
The Australian Government has introduced legislation that requires ISPs to "restrict access to age restricted content (commercial MA15+ content and R18+ content) either hosted in Australia or provided from Australia" that was due to commence from 20 January 2008, known asCleanfeed.[24]
Cleanfeed is a proposed mandatory ISP level content filtration system. It was proposed by theBeazley ledAustralian Labor Party opposition in a 2006 press release, with the intention of protecting children who were vulnerable due to claimed parental computer illiteracy. It was announced on 31 December 2007 as a policy to be implemented by theRudd ALP government, and initial tests inTasmania have produced a 2008 report. Cleanfeed is funded in the current budget, and is moving towards an Expression of Interest for live testing with ISPs in 2008. Public opposition and criticism have emerged, led by theEFA and gaining irregular mainstream media attention, with a majority of Australians reportedly "strongly against" its implementation.[25] Criticisms include its expense, inaccuracy (it will be impossible to ensure only illegal sites are blocked) and the fact that it will be compulsory, which can be seen as an intrusion on free speech rights.[25] Another major criticism point has been that although the filter is claimed to stop certain materials, the underground rings dealing in such materials will not be affected. The filter might also provide a false sense of security for parents, who might supervise children less while using the Internet, achieving the exact opposite effect.[original research?] Cleanfeed is a responsibility ofSenator Conroy's portfolio.
InDenmark it is stated policy that it will "prevent inappropriate Internet sites from being accessed from children's libraries across Denmark".[26] "'It is important that every library in the country has the opportunity to protect children against pornographic material when they are using library computers. It is a main priority for me as Culture Minister to make sure children can surf the net safely at libraries,' states Brian Mikkelsen in a press-release of the Danish Ministry of Culture."[27]
Many libraries in the UK such as theBritish Library[28] andlocal authoritypublic libraries[29] apply filters to Internet access. According to research conducted by the Radical Librarians Collective, at least 98% of public libraries apply filters; including categories such as "LGBT interest", "abortion" and "questionable".[30] Some public libraries blockPayday loan websites[31]
The use of Internet filters or content-control software varies widely in public libraries in the United States, since Internet use policies are established by the local library board. Many libraries adopted Internet filters after Congress conditioned the receipt of universal service discounts on the use of Internet filters through theChildren's Internet Protection Act (CIPA). Other libraries do not install content control software, believing that acceptable use policies and educational efforts address the issue of children accessingage-inappropriate content while preserving adult users' right to freely access information. Some libraries use Internet filters on computers used by children only. Some libraries that employ content-control software allow the software to be deactivated on a case-by-case basis on application to a librarian; libraries that are subject to CIPA are required to have a policy that allows adults to request that the filter be disabled without having to explain the reason for their request.
Many legal scholars believe that a number of legal cases, in particularReno v. American Civil Liberties Union, established that the use of content-control software in libraries is a violation of the First Amendment.[32] The Children's Internet Protection Act [CIPA] and the June 2003 caseUnited States v. American Library Association found CIPA constitutional as a condition placed on the receipt of federal funding, stating that First Amendment concerns were dispelled by the law's provision that allowed adult library users to have the filtering software disabled, without having to explain the reasons for their request. The plurality decision left open a future "as-applied" Constitutional challenge, however.
In November 2006, a lawsuit was filed against the North Central Regional Library District (NCRL) in Washington State for its policy of refusing to disable restrictions upon requests of adult patrons, but CIPA was not challenged in that matter.[33] In May 2010, the Washington State Supreme Court provided an opinion after it was asked to certify a question referred by the United States District Court for the Eastern District of Washington: "Whether a public library, consistent with Article I, § 5 of the Washington Constitution, may filter Internet access for all patrons without disabling Web sites containing constitutionally-protected speech upon the request of an adult library patron." The Washington State Supreme Court ruled that NCRL's internet filtering policy did not violate Article I, Section 5 of the Washington State Constitution. The Court said: "It appears to us that NCRL's filtering policy is reasonable and accords with its mission and these policies and is viewpoint neutral. It appears that no article I, section 5 content-based violation exists in this case. NCRL's essential mission is to promote reading and lifelong learning. As NCRL maintains, it is reasonable to impose restrictions on Internet access in order to maintain an environment that is conducive to study and contemplative thought." The case returned to federal court.
In March 2007, Virginia passed a law similar to CIPA that requires public libraries receiving state funds to use content-control software. Like CIPA, the law requires libraries to disable filters for an adult library user when requested to do so by the user.[34]
Utilizing a filter that is overly zealous at filtering content, or mislabels content not intended to be censored can result in over-blocking, or over-censoring. Overblocking can filter out material that should be acceptable under the filtering policy in effect, for example health related information may unintentionally be filtered along withporn-related material because of theScunthorpe problem. Filter administrators may prefer to err on the side of caution by accepting over blocking to prevent any risk of access to sites that they determine to be undesirable. Content-control software was mentioned as blocking access to Beaver College before its name change toArcadia University.[35] Another example was the filtering ofHorniman Museum.[36] As well, over-blocking may encourage users to bypass the filter entirely.
Whenever new information is uploaded to the Internet, filters can under block, or under-censor, content if the parties responsible for maintaining the filters do not update them quickly and accurately, and a blacklisting rather than a whitelisting filtering policy is in place.[37]
Many[38] would not be satisfied with government filtering viewpoints on moral or political issues, agreeing that this could become support forpropaganda. Many[39] would also find it unacceptable that an ISP, whether by law or by the ISP's own choice, should deploy such software without allowing the users to disable the filtering for their own connections. In the United States, theFirst Amendment to the United States Constitution has been cited in calls to criminalise forced internet censorship. (Seesection below)
Many types of content-control software have been shown to block sites based on the religious and political leanings of the company owners. Examples include blocking several religious sites[40][41] (including the Web site of the Vatican), many political sites, and homosexuality-related sites.[42]X-Stop was shown to block sites such as theQuaker web site, theNational Journal of Sexual Orientation Law,The Heritage Foundation, and parts ofThe Ethical Spectacle.[43] CYBERsitter blocks out sites likeNational Organization for Women.[44] Nancy Willard, an academic researcher and attorney, pointed out that many U.S. public schools and libraries use the same filtering software that many Christian organizations use.[45] Cyber Patrol, a product developed by The Anti-Defamation League and Mattel's The Learning Company,[46] has been found to block not only political sites it deems to be engaging in 'hate speech' but also human rights web sites, such as Amnesty International's web page about Israel and gay-rights web sites, such as glaad.org.[47]
In 1998, a United States federal district court in Virginia ruled (Loudoun v. Board of Trustees of the Loudoun County Library) that the imposition of mandatory filtering in a public library violates the First Amendment.[48]
In 1996 the US Congress passed theCommunications Decency Act, banning indecency on the Internet. Civil liberties groups challenged the law under the First Amendment, and in 1997 theSupreme Court ruled in their favor.[49] Part of the civil liberties argument, especially from groups like theElectronic Frontier Foundation,[50] was that parents who wanted to block sites could use their own content-filtering software, making government involvement unnecessary.[51]
In the late 1990s, groups such as the Censorware Project began reverse-engineering the content-control software and decrypting the blacklists to determine what kind of sites the software blocked. This led to legal action alleging violation of the "Cyber Patrol"license agreement.[52] They discovered that such tools routinely blocked unobjectionable sites while also failing to block intended targets.
Some content-control software companies responded by claiming that their filtering criteria were backed by intensive manual checking. The companies' opponents argued, on the other hand, that performing the necessary checking would require resources greater than the companies possessed and that therefore their claims were not valid.[53]
TheMotion Picture Association successfully obtained a UK ruling enforcing ISPs to use content-control software to preventcopyright infringement by their subscribers.[54]
Content filtering in general can "be bypassed entirely by tech-savvy individuals." Blocking content on a device "[will not]…guarantee that users won't eventually be able to find a way around the filter."[55] Content providers may changeURLs orIP addresses to circumvent filtering. Individuals with technical expertise may use a different method by employing multiple domains or URLs that direct to a shared IP address where restricted content is present. This strategy doesn't circumventIP packet filtering, however can evadeDNS poisoning andweb proxies. Additionally, perpetrators may use mirrored websites that avoid filters.[56]
Some software may be bypassed successfully by using alternative protocols such asFTP ortelnet orHTTPS, conducting searches in a different language, using aproxy server or a circumventor such asPsiphon. Also cached web pages returned by Google or other searches could bypass some controls as well. Web syndication services may provide alternate paths for content. Some of the more poorly designed programs can be shut down by killing their processes: for example, inMicrosoft Windows through the WindowsTask Manager, or inMac OS X using Force Quit orActivity Monitor. Numerous workarounds and counters to workarounds from content-control software creators exist.Google services are often blocked by filters, but these may most often be bypassed by usinghttps:// in place ofhttp:// since content filtering software is not able to interpret content under secure connections (in this case SSL).[needs update]
An encryptedVPN can be used as means of bypassing content control software, especially if the content control software is installed on an Internet gateway or firewall. Other ways to bypass a content control filter include translation sites andestablishing a remote connection with an uncensored device.[57]
