Cisco Cisco Email Security Appliance C650 Guía Del Usuario
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Cisco AsyncOS 9.1 for Email User Guide
Chapter 9 Using Message Filters to Enforce Email Policies
Attachment Scanning
For more information, see
.
Examples of Attachment Scanning Message Filters
The following examples shows actions performed on attachments:
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Inserting Headers
In these examples, AsyncOS inserts headers when the attachments contain specified content.
In the following example, all of the attachments on the message are scanned for a keyword. If the
keyword is present in all of the attachments, a custom X-Header is inserted:
keyword is present in all of the attachments, a custom X-Header is inserted:
In the following example, the attachment is scanned for a pattern in the binary data. The filter uses the
attachment-binary-contains
filter rule to search for a pattern that indicates that the PDF document is
encrypted. If the pattern is present in the binary data, a custom header is inserted:
Dropping Attachments by File Type
In the following example, the “executable” group of attachments (
.exe
,
.dll
, and
.scr
) is stripped from
messages and text is added to the message, listing the filenames of the dropped files (via the
$dropped_filename
action variable). Note that the
drop-attachments-by-filetype
action examines
attach_disclaim:
if (every-attachment-contains('[dD]isclaimer') ) {
insert-header("X-Example-Approval", "AttachOK");
}
match_PDF_Encrypt:
if (attachment-filetype == 'pdf' AND
attachment-binary-contains('/Encrypt')){
strip-header (‘Subject’);
insert-header (‘Subject’, ‘[Encrypted] $Subject’);
}