User Guide

Contents
vii
AsyncOS 9.1.2 for Cisco Email Security Appliances User Guide
Message Filter Example Syntax 9-3
Message Filter Processing 9-4
Message Filter Order 9-4
Message Header Rules and Evaluation 9-5
Message Bodies vs. Message Attachments 9-5
Thresholds for Matches in Content Scanning 9-6
AND Test and OR Tests in Message Filters 9-9
Message Filter Rules 9-10
Filter Rules Summary Table 9-10
Regular Expressions in Rules 9-16
Smart Identifiers 9-20
Description and Examples of Message Filter Rules 9-22
Message Filter Actions 9-48
Filter Actions Summary Table 9-48
Action Variables 9-55
Matched Content Visibility 9-57
Description and Examples of Message Filter Actions 9-57
Attachment Scanning 9-75
Message Filters for Scanning Attachments 9-76
Image Analysis 9-77
Configuring the Image Analysis Scanning Engine 9-77
Configuring the Message Filter to Perform Actions Based on Image Analysis Results 9-81
Notifications 9-83
Examples of Attachment Scanning Message Filters 9-83
Using the CLI to Manage Message Filters 9-87
Creating a New Message Filter 9-88
Deleting a Message Filter 9-89
Moving a Message Filter 9-89
Activating and Deactivating a Message Filter 9-89
Importing Message Filters 9-93
Exporting Message Filters 9-93
Viewing Non-ASCII Character Sets 9-93
Displaying a Message Filter List 9-94
Displaying Message Filter Details 9-94
Configuring Filter Log Subscriptions 9-94
Changing Message Encoding 9-96
Sample Message Filters 9-98
Message Filter Examples 9-104
Open-Relay Prevention Filter 9-104