User Guide

17-16
AsyncOS 9.1.2 for Cisco Email Security Appliances User Guide
Chapter 17 Data Loss Prevention
DLP Policies for RSA Email DLP
Related Topics
• Examples of Regular Expressions for Identifying Identification Numbers, page 17-16
Examples of Regular Expressions for Identifying Identification Numbers
Simple regular expressions that describe patterns of numbers and letters in identification or account
numbers might look like the following:
Element Description
Regular expression (abc)
Regular expressions for classifiers match a string if the
sequence of directives in the regular expression match any
part of the string.
For example, the regular expression
ACC matches the string
ACCOUNT as well as ACCT.
[ ]
Use brackets to indicate a set of characters. Characters can
defined individually or within a range.
For example,
[a-z] matches all lowercase letters from a to z,
while
[a-zA-Z] matches all uppercase and lowercase letters
from
A to Z. [xyz] matches only the letters x, y, or z.
Backslash special characters (\)
The backslash character escapes special characters. 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.
The backslash character also begins tokens, such as
\d.
Important Note: The backslash is also a special escape
character for the parser. As a result, if you want to include a
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.
\d
Token that matches a digit (0-9). To match more than one
digit, enter an integer in
{} to define the length of the number.
For example,
\d matches only a single digit such as 5, but not
55. Using \d{2} matches a number consisting of two digits,
such as
55, but not 5.
Number of repetitions {min,max}
The regular expression notation that indicates the number of
repetitions of the previous token is supported.
For example, the expression “
\d{8}” matches 12345678 and
11223344 but not 8.
Or (|)
Alternation, or the “or” operator. If A and B are regular
expressions, the expression “
A|B” will match any string that
matches either “A” or “B.” Can be used to combine number
patterns in a regular expression.
For example, the expression “
foo|bar” will match either foo
or
bar, but not foobar.