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Web Protection Frequently Asked Questions : How do keywords and regular expressions work?
How do keywords and regular expressions work?
Web Protection FAQ | Web Protection Solutions | v8.2.x, v8.3.x | 16-Dec-2016
Keywords and regular expressions are ways to identify types or groups of related URLs for special handling.
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A keyword is a string of characters (a word, phrase, number, or acronym) that might be found in a URL.
When you create a keyword, you associate it with a category. When your software finds that keyword in a URL, it assigns the URL to the category that you have selected, and blocks the URL.
Keywords are used only to recategorize and block URLs; they cannot be used to permit URLs.
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A regular expression is a template or pattern used to match multiple strings, or groups of characters. Regular expressions can be used:
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To identify groups of related URLs in limited access filters and exceptions
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As a more flexible form of keyword, to assign URLs to categories for blocking
When you use regular expressions, Filtering Service tries to match the general pattern, rather than a specific, single URL or keyword. Regular expressions match precise terms and are case sensitive.
Use keywords and regular expression with caution to avoid unintended over blocking or under blocking.
More about keywords
There are two steps involved in using keywords:
1.
Define specific keywords and associate them with categories.
2.
Turn on keyword-based blocking in some or all of your policies.
Once keyword-based blocking is enabled, web protection software tries to match the keyword against each requested URL as follows:
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If the keyword contains only ASCII characters, the keyword is matched against the domain, path, and query (CGI) portions of a URL. The match is case independent.
For example, if you associated the keyword "nba" with the permitted Sports category, the following URLs are blocked:
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sports.espn.go.com/nba/
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modernbakery.com
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fashionbar.com
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If the keyword contains characters outside the ASCII character set, the keyword is matched against only the path and query (CGI) portions of the string. The match is case independent.
For example, if you associated the keyword "fútbol" with the permitted Sports category:
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"www.fútbol.com" is permitted (the domain portion of the URL is not matched).
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"es.wikipedia.org/wiki/Fútbol" is blocked (the path portion of the URL is matched).
When web protection software identifies a keyword in a URL:
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The URL is recategorized according to the keyword match.
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Reports show the keyword category, rather than the Master Database category, for the URL.
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The block page the user receives shows that the URL was blocked by keyword.
For more information on using and defining keywords see your Administrator Help (version 8.3 or version 8.2).
More about regular expressions
Regular expressions can be as simple or complex as your environment requires, but use them with care. Poorly constructed regular expressions can result in excessive filtering overhead.
As with keywords, if non-ASCII characters appear in a regular expression, the expression is matched against only the path and query (CGI) strings in the URL. No matching is done against the domain.
If only ASCII characters appear in the regular expression, the match is performed against the entire URL.
Most Perl regular expression syntax is supported.
For further help with regular expressions, see:
en.wikipedia.org/wiki/Regular_expression
www.regular-expressions.info/

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Web Protection Frequently Asked Questions : How do keywords and regular expressions work?
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