Types of Internet Filters:
Internet filtering software uses algorithms, or patterns, that check website addresses and pages for images or words that depict graphic violence, have sexual content, contain racial slurs or epithets (or other related hate content), and other content deemed inappropriate by parents (political web sites, gambling and alcohol-related sites). There are three distinct types of Internet filters.
Black List Filters
Black list filters are the most popular types of Internet blocking software. A website is added to a black list (“bad” list) that keeps track of content with objectionable words and images. When a user tries to access the website address on their browser, the software compares the address to the addresses on the list. If there is a match, the users are denied access to the requested website.
White List Filters
White list filters allow access only to “good” sites on the list while denying access to websites not on the list. White list filters are the most restrictive blockers.
Keyword or Content Filters
Keyword or content lists scan websites for the presence of specific words, phrases, or images that appear on the restricted list. Access to a website is denied if the keyword or content matches any words on the list. Because of the specificity of the filter, these programs often deny access to websites that have acceptable content.
Content Rating Systems
Webmasters provide a classification of a website based on its content. Website classifications are voluntary and are based on the web developer’s description of their online content.
Work Place Web Filtering PDF Document
Web Filtering Technologies PDF Document
Smoothwall UTM-3000 PDF Document
Smoothwall UTM(Unified Threat Management) Guide PDF
Network and CyberSecurity Professional 
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