Cisco Cisco Email Security Appliance C170 Guía Del Usuario
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AsyncOS 9.1.2 for Cisco Email Security Appliances User Guide
Chapter 9 Using Message Filters to Enforce Email Policies
Message Filter Rules
Attachment Filename Rule
The
attachment-filename
rule checks the filenames of each attachment in a message to see if it matches
the given regular expression. This comparison is case-sensitive. The comparison is, however sensitive to
whitespace so if the filename has encoded whitespace at the end, the filter will skip the attachment. If
one of the message’s attachments matches the filename, this rule returns “true.”
whitespace so if the filename has encoded whitespace at the end, the filter will skip the attachment. If
one of the message’s attachments matches the filename, this rule returns “true.”
Please note the following points:
•
Each attachment’s filename is captured from the MIME headers. The filename in the MIME header
may contain trailing spaces.
may contain trailing spaces.
•
If an attachment is an archive, the Cisco appliance will harvest the filenames from inside the archive,
and apply scan configuration rules (see
and apply scan configuration rules (see
) accordingly.
–
If the attachment is a single compressed file (despite the file extension), it is not considered an
archive and the filename of the compressed file is not harvested. This means that the file is not
processed by the
archive and the filename of the compressed file is not harvested. This means that the file is not
processed by the
attachment-filename
rule. An example of this type of file is an executable
file (.exe) compressed with
gzip
.
–
For attachments consisting of a single compressed file, such as foo.exe.gz, use regular
expression to search for specific file types within compressed files. See
expression to search for specific file types within compressed files. See
See
for more information on message filter rules you can use to
manipulate attachments to messages.
The following filter checks all email sent through the listener, and if a message contains an attachment
with a filename
with a filename
*.mp3
, the message is bounced:
Related Topics
•
Attachment Filenames and Single Compressed Files within Archive Files
This example shows how to match single compressed files in archives such as those created by
gzip
:
bounce();
}
block_mp3s:
if (attachment-filename == '(?i)\\.mp3$') {
bounce();
}
quarantine_gzipped_exe_or_pif:
if (attachment-filename == '(?i)\\.(exe|pif)($|.gz$)') {