Cisco Cisco Email Security Appliance C650 Guía Del Usuario
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Cisco IronPort AsyncOS 7.5 for Email Configuration Guide
OL-25136-01
Chapter 14 Text Resources
headers, and message attachments for terms included in the dictionary in order to
take appropriate action in accordance with your corporate policies. For example,
you could create a list of confidential or profane words, and, using a filter rule to
scan messages that contain words in the list, drop, archive, or quarantine the
message.
take appropriate action in accordance with your corporate policies. For example,
you could create a list of confidential or profane words, and, using a filter rule to
scan messages that contain words in the list, drop, archive, or quarantine the
message.
The AsyncOS operating system includes the ability to define a total of 100 content
dictionaries using the GUI (Mail Policies > Dictionaries) or the CLI’s
dictionaries using the GUI (Mail Policies > Dictionaries) or the CLI’s
dictionaryconfig
command. You can create, delete, and view dictionaries; add
and delete entries from a dictionary; and import and export entire dictionaries.
Dictionary Content
Words in dictionaries are created with one text string per line, and entries can be
in plain text or in the form of regular expressions. Dictionaries can also contain
non-ASCII characters. Defining dictionaries of regular expressions can provide
more flexibility in matching terms, but doing so requires you to understand how
to delimit words properly. For a more detailed discussion of Python style regular
expressions, consult the Python Regular Expression HOWTO, accessible from
in plain text or in the form of regular expressions. Dictionaries can also contain
non-ASCII characters. Defining dictionaries of regular expressions can provide
more flexibility in matching terms, but doing so requires you to understand how
to delimit words properly. For a more detailed discussion of Python style regular
expressions, consult the Python Regular Expression HOWTO, accessible from
http://www.python.org/doc/howto/
Note
To use the special character # at the beginning of a dictionary entry, you can use
a character class [#] to prevent it being treated as a comment.
a character class [#] to prevent it being treated as a comment.
For each term, you specify a “weight,” so that certain terms can trigger filter
conditions more easily. When AsyncOS scans messages for the content dictionary
terms, it “scores” the message by multiplying the number of term instances by the
weight of term. Two instances of a term with a weight of three would result in a
score of six. AsyncOS then compares this score with a threshold value associated
with the content or message filter to determine if the message should trigger the
filter action.
conditions more easily. When AsyncOS scans messages for the content dictionary
terms, it “scores” the message by multiplying the number of term instances by the
weight of term. Two instances of a term with a weight of three would result in a
score of six. AsyncOS then compares this score with a threshold value associated
with the content or message filter to determine if the message should trigger the
filter action.
You can also add smart identifiers to a content dictionary. Smart identifiers are
algorithms that search for patterns in data that correspond to common numeric
patterns, such as social security numbers and ABA routing numbers. These
identifiers can useful for policy enforcement. For more information about regular
expressions, see “Regular Expressions in Rules” in the “Using Message Filters to
Enforce Email Policies” chapter of the Cisco IronPort AsyncOS for Email
algorithms that search for patterns in data that correspond to common numeric
patterns, such as social security numbers and ABA routing numbers. These
identifiers can useful for policy enforcement. For more information about regular
expressions, see “Regular Expressions in Rules” in the “Using Message Filters to
Enforce Email Policies” chapter of the Cisco IronPort AsyncOS for Email