Cisco Cisco Email Security Appliance C190 Guía Del Usuario
6-23
Cisco IronPort AsyncOS 7.5 for Email Advanced Configuration Guide
OL-25137-01
Chapter 6 Using Message Filters to Enforce Email Policies
Asterisk (
*
) directive
Rules containing an asterisk (
*
) match “zero or more
matches of the previous directive.” In particular, the
sequence of a period and an asterisk (
sequence of a period and an asterisk (
.*
) matches any
sequence of characters (not containing a new line).
For example, the regular expression
^P.*Piper$
matches all of these strings:
PPiper
,
Peter Piper
,
P.Piper
,
and
Penelope Penny Piper
.
Backslash special
characters (
characters (
\
)
The backslash character escapes special characters.
Thus the sequence
Thus the sequence
\.
only matches a literal period, the
sequence
\$
only matches a literal dollar sign, and the
sequence
\^
only matches a literal caret symbol. For
example, the regular expression
^ik\.ac\.uk$
only
matches the string
ik.ac.uk
.
Important Note: The backslash is also a special
escape character for the parser. As a result, if you want
to include backslash in your regular expression, you
must use two backslashes — so that after parsing, only
one “real” backslash remains, which is then passed to
the regular expression system. So, if you wanted to
match the example domain above, you would enter
escape character for the parser. As a result, if you want
to include backslash in your regular expression, you
must use two backslashes — so that after parsing, only
one “real” backslash remains, which is then passed to
the regular expression system. So, if you wanted to
match the example domain above, you would enter
^ik\\.ac\\.uk$
.
Case-insensitivity (
(?i)
)
The token
(?i)
that indicates the rest of the regular
expression should be treated in case-insensitive mode.
Placing this token at the beginning of a case-sensitive
regular expression results in a completely insensitive
match.
Placing this token at the beginning of a case-sensitive
regular expression results in a completely insensitive
match.
For example, the regular expression “
(?i)viagra
”
matches
Viagra
,
vIaGrA
, and
VIAGRA
.
Table 6-3
Regular Expression in Rules