Overview

Security filtering is clearly the sine qua non of a product called the Email Security Appliance (ESA). This chapter explores the security filtering features—like anti-spam and antivirus—in depth. It also covers the zero-day virus capabilities of the Cisco Outbreak Filters feature and the use of other features, like content filters for security purposes.

The goal is to eliminate all kinds of unwanted messages from the environment entirely. At the very least, these junk messages are time-wasting, aggravating, and intrusive. At worst, they can be extremely dangerous—malicious software attached to, or linked from, email messages can be used for security breaches, allowing an attacker inside access to networks and servers in your organization.