TRITON - Web Security Help, Version 7.7 - Websense

Refine Filtering PoliciesUsing regular expressionsTRITON - Web Security Help | Web Security Solutions | Version 7.7.xA regular expression is a template or pattern used to match multiple strings, orgroups of characters. You can use regular expressions in limited access filters, or todefine custom URLs or keywords. Filtering Service then tries to match the generalpattern, rather than a specific, single URL or keyword.Consider this simple regular expression:domain.(com|org|net)This expression pattern matches the URLs:domain.comdomain.orgdomain.netUse regular expressions with caution. They provide a powerful filtering tool, but caneasily result in either unexpected over blocking or under blocking. Also, poorlyconstructed regular expressions can result in excessive filtering overhead.ImportantUsing regular expressions as filtering criteria may increaseCPU usage. Tests have shown that with 100 regularexpressions, the average CPU usage on the FilteringService machine increased by 20%.As with keywords, when non-ASCII characters appear in a regular expression, theexpression is matched against only the path and query strings in a URL, and not thedomain (“www.domain.com/path?query”).Websense software supports most Perl regular expression syntax, with 2 exceptions.The unsupported syntax is unlikely to be useful for matching strings that could befound in a URL.Unsupported regular expression syntax includes:(?{code})??{code})For further help with regular expressions, see:en.wikipedia.org/wiki/Regular_expressionwww.regular-expressions.info/290 Websense Web Security Solutions