Implementing undesirable URL protection on a Cisco Email Security Appliance (ESA) requires the integration of two specific security services. First, Anti-Spam scanning (C) must be enabled, as the anti-spam engine is responsible for scanning the message body and headers to identify URLs. Once identified, these URLs are passed to the URL filtering service. Second, Outbreak Filters (A) must be enabled to provide advanced, real-time protection. Outbreak Filters checks URLs against reputation data and can rewrite them, redirecting user clicks through a Cisco security proxy for analysis, which is a core component of protecting against malicious and undesirable links.

B. Enable email relay: This is a fundamental function for the appliance to process any mail, not a specific prerequisite for the URL protection feature itself.

D. Enable port bouncing: This is an unrelated network-level technique and not a configurable prerequisite for a security service within the Cisco ESA.

E. Enable antivirus scanning: While often used in conjunction, the antivirus engine is a separate component focused on file attachments and is not a direct dependency for URL filtering.

1. Cisco AsyncOS 14.0 for Email Security User Guide

Chapter: "URL Filtering"

Section: "Overview of URL Filtering". The documentation states

"URL filtering is integrated with the anti-spam scanning engine." This directly confirms that Anti-Spam scanning is a prerequisite.

2. Cisco AsyncOS 14.0 for Email Security User Guide

Chapter: "Protecting Against Viruses

Malware

and Other Threats"

Section: "How Outbreak Filters Work". This section details the URL rewriting and analysis function: "Outbreak Filters can rewrite URLs in messages... When the user clicks the rewritten URL

the Cisco Web Security Proxy is contacted." This functionality is central to undesirable URL protection

making Outbreak Filters a necessary component.

3. Cisco Email Security Appliance Configuration Guide

Release 12.0

Chapter: "Configuring URL Filtering"

Section: "Enabling and Configuring URL Filtering". The guide explicitly lists as a prerequisite: "Before you begin: Enable Anti-Spam scanning on the appliance." This provides direct evidence for the requirement of Anti-Spam.