Fortinet 100A Regular expression vs. wildcard match pattern, Word boundary, Case sensitivity, 336

Configuring the banned word list Spam filter

Regular expression vs. wildcard match pattern

In Perl regular expressions, ‘.’ character refers to any single character. It is similar to the ‘?’ character in wildcard match pattern. As a result:

•fortinet.com not only matches fortinet.com but also matches fortinetacom, fortinetbcom, fortinetccom and so on.

To match a special character such as '.' and ‘*’ use the escape character ‘\’. For example:

•To mach fortinet.com, the regular expression should be: fortinet\.com

In Perl regular expressions, ‘*’ means match 0 or more times of the character before it, not 0 or more times of any character. For example:

•forti*\.com matches fortiiii.com but does not match fortinet.com

To match any character 0 or more times, use ‘.*’ where ‘.’ means any character and the ‘*’ means 0 or more times. For example, the wildcard match pattern forti*.com should therefore be fort.*\.com.

Word boundary

In Perl regular expressions, the pattern does not have an implicit word boundary. For example, the regular expression “test” not only matches the word “test” but also matches any word that contains the “test” such as “atest”, “mytest”, “testimony”, “atestb”. The notation “\b” specifies the word boundary. To match exactly the word “test”, the expression should be \btest\b.

Case sensitivity

Regular expression pattern matching is case sensitive in the Web and Spam filters. To make a word or phrase case insensitive, use the regular expression /i For example, /bad language/i will block all instances of “bad language” regardless of case.

Table 30: Perl regular expression formats

Expression	Matches
abc	abc (that exact character sequence, but anywhere in the string)
^abc	abc at the beginning of the string
abc$	abc at the end of the string
ab	either of a and b
^abcabc$	the string abc at the beginning or at the end of the string
ab{2,4}c	an a followed by two, three or four b's followed by a c
ab{2,}c	an a followed by at least two b's followed by a c
ab*c	an a followed by any number (zero or more) of b's followed by a c
ab+c	an a followed by one or more b's followed by a c
ab?c	an a followed by an optional b followed by a c; that is, either abc or ac
a.c	an a followed by any single character (not newline) followed by a c
a\.c	a.c exactly
[abc]	any one of a, b and c

336 01-28007-0068-20041203 Fortinet Inc.