Editing Internet filter (section)

==Types of filtering==
Filters can be implemented in many different ways: by software on a personal computer, via network infrastructure such as [[proxy server]]s, [[Domain Name System|DNS]] servers, or [[Firewall (computing)|firewall]]s 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.

=== Browser based filters ===
:Browser based content filtering solution is the most lightweight solution to do the content filtering, and is implemented via a third party [[browser extension]].

=== E-mail filters ===
:E-mail filters act on information contained in the mail body, in the mail headers such as sender and subject, and e-mail attachments to classify, accept, or reject messages. [[Bayesian spam filtering|Bayesian filters]], a type of statistical filter, are commonly used. Both client and server based filters are available.

=== Client-side filters ===
:This type of filter is installed as software on each computer where filtering is required.<ref>{{cite book|url=http://www.nap.edu/netsafekids/pro_fm_filter.html|title=Client-side filters|series=NetSafeKids|publisher=[[National Academy of Sciences]]|year=2003|isbn=9780309082747|access-date=24 June 2013}}</ref><ref>{{cite web|url=http://windows.microsoft.com/en-us/windows-vista/Protecting-your-kids-with-Family-Safety|title=Protecting Your Kids with Family Safety|access-date=10 July 2012|website=[[microsoft]].com}}</ref> This filter can typically be managed, disabled or uninstalled by anyone who has administrator-level privileges on the system. A DNS-based client-side filter would be to set up a [[DNS Sinkhole]], such as [[Pi-Hole]].

=== Content-limited (or filtered) ISPs ===
:Content-limited (or filtered) ISPs are Internet service providers that offer access to only a set portion of Internet content on an opt-in or a mandatory basis. Anyone who subscribes to this type of service is subject to restrictions. The type of filters can be used to implement government,<ref>{{cite web|url=http://pam2011.gatech.edu/papers/pam2011--Xu.pdf|title=Internet Censorship in China: Where Does the Filtering Occur?|first1=Xueyang|last1=Xu|first2=Z. Morley|last2=Mao|author2-link=Z. Morley Mao|first3=J. Alex|last3=Halderman|publisher=[[University of Michigan]]|website=[[Georgia Tech]]|date=5 Jan 2011|access-date=10 July 2012|archive-url=https://web.archive.org/web/20120324172922/http://pam2011.gatech.edu/papers/pam2011--Xu.pdf|archive-date=24 March 2012|url-status=dead}}</ref> regulatory<ref>{{cite web|url=https://www.telegraph.co.uk/technology/broadband/9242729/The-Pirate-Bay-cut-off-from-millions-of-Virgin-Media-customers.html|title=The Pirate Bay cut off from millions of Virgin Media customers|author=Christopher Williams|date=3 May 2012|access-date=8 May 2012|website=[[The Daily Telegraph]]}}</ref> or parental control over subscribers.

=== Network-based filtering ===
:This type of filter is implemented at the [[transport layer]] as a [[transparent proxy]], or at the [[application layer]] as a [[proxy server|web proxy]].<ref>{{cite web|url=http://www.websense.com/content/support/library/web/v75/wcg_deploy/WCG_Deploy.1.3.aspx|title=Explicit and Transparent Proxy Deployments|website=[[websense]].com|access-date=30 March 2012|year=2010|url-status=dead|archive-url=https://web.archive.org/web/20120418150020/http://www.websense.com/content/support/library/web/v75/wcg_deploy/WCG_Deploy.1.3.aspx|archive-date=18 April 2012}}</ref> Filtering software may include [[data loss prevention software|data loss prevention]] functionality to filter outbound as well as inbound information. All users are subject to the access policy defined by the institution. The filtering can be customized, so a school district's high school library can have a different filtering profile than the district's junior high school library.

=== DNS-based filtering ===
:This type of filtering is implemented at the DNS layer and attempts to prevent lookups for domains that do not fit within a set of policies (either parental control or company rules). Multiple free [[Public recursive name server|public DNS services]] offer filtering options as part of their services. [[DNS Sinkhole]]s such as [[Pi-Hole]] can be also be used for this purpose, though client-side only.<ref>{{Cite web |last=Fruhlinger |first=Keith Shaw and Josh |date=2022-07-13 |title=What is DNS and how does it work? |url=https://www.networkworld.com/article/3268449/what-is-dns-and-how-does-it-work.html |access-date=2023-08-22 |website=Network World |language=en}}</ref>

=== Search-engine filters ===
:Many [[search engine]]s, such as [[Google Search|Google]] and [[Microsoft Bing|Bing]] offer users the option of turning on a safety filter. When this safety filter is activated, it filters out the inappropriate links from all of the search results. If users know the actual URL of a website that features explicit or adult content, they have the ability to access that content without using a search engine. Some providers offer child-oriented versions of their engines that permit only child friendly websites.<ref>{{cite book|url=http://www.nap.edu/netsafekids/pro_fm_filter.html|title=Filtering|series=NetSafeKids|publisher=[[National Academy of Sciences]]|year=2003|isbn=9780309082747|access-date=22 November 2010}}</ref>