Implementing Mimecast Targeted Attack Protection

Implementing Mimecast Targeted Attack Protection

Overview

Mimecast Targeted Threat Protection (TTP) is a suite of advanced email security services designed to protect against sophisticated phishing, spearphishing, and targeted attacks. TTP consists of four core modules: URL Protect (real-time URL rewriting and click-time analysis), Attachment Protect (sandbox detonation of suspicious attachments), Impersonation Protect (BEC and whaling detection), and Internal Email Protect (scanning internal/outbound email for threats). As of November 2025, Mimecast enabled URL Pre-Delivery Action with Hold setting for all customers by default.

When to Use

Trigger phrases:

• "implementing mimecast targeted attack protection"

• "Deploy Mimecast Targeted Threat Protection including URL Protect, Attachment Pro"

• When deploying or configuring implementing mimecast targeted attack protection capabilities in your environment

• When establishing security controls aligned to compliance requirements

• When building or improving security architecture for this domain

• When conducting security assessments that require this implementation

Prerequisites

• Mimecast Email Security license with TTP add-on
• Administrative access to Mimecast Administration Console
• Microsoft 365 or Google Workspace environment
• MX records configured to route through Mimecast
• Understanding of email authentication (SPF, DKIM, DMARC)

Key Concepts

This section covers key concepts for implementing mimecast targeted attack protection.

• Ensure all prerequisites are met before proceeding
• Follow the documented workflow steps in sequence
• Record results and any anomalies encountered during this phase

TTP Module Overview

Impersonation Protection Scenarios

• Hit 3 (Default): Flags emails matching 3+ impersonation indicators
• Hit 1 (VIP): Flags emails matching 1+ indicator for designated VIP users
• Key identifiers: display name similarity, domain similarity, reply-to mismatch, newly registered domains

URL Protect Modes

• Rewrite: URLs rewritten to route through Mimecast proxy at click time
• Pre-Delivery Action (Hold): URLs checked before message delivery; held if suspicious
• Pre-Delivery Action (None): URLs checked pre-delivery but not held

Workflow

# Example: IOC detection
import re

IOC_PATTERNS = {
    "ip": r"\b(?:\d{1,3}\.){3}\d{1,3}\b",
    "domain": r"\b[a-z0-9-]+\.[a-z]{2,}\b",
    "hash_md5": r"\b[a-f0-9]{32}\b",
    "hash_sha256": r"\b[a-f0-9]{64}\b",
}

def extract_iocs(text: str) -> dict:
    return {k: re.findall(v, text) for k, v in IOC_PATTERNS.items()}

1. Scope and authorize — confirm written authorization and define target boundaries
2. Reconnaissance — enumerate targets, services, and potential attack surfaces
3. Exploitation — attempt exploitation of identified vulnerabilities within scope
4. Post-exploitation — document access level, lateral movement, and data exposure
5. Report and remediate — compile findings with reproduction steps and fix recommendations

Step 1: Configure URL Protect Policy

• Navigate to Administration > Gateway > Policies > Targeted Threat Protection - URL Protect
• Create URL Protect definition with rewriting enabled for inbound messages
• Enable URL Pre-Delivery Action set to "Hold" for maximum protection
• Configure scan mode: aggressive for high-risk users, moderate for general population
• Set action for malicious URLs: block page with user notification
• Enable URL logging for all click events

Step 2: Configure Attachment Protect Policy

• Navigate to Administration > Gateway > Policies > Targeted Threat Protection - Attachment Protect
• Create Attachment Protect definition for inbound email
• Select sandbox mode: "Safe File" (converts to safe format) or "Dynamic Configuration" (full sandbox)
• Configure attachment types to scan: executables, Office documents, PDFs, archives
• Set timeout for sandbox analysis (default: up to 7 minutes for complex files)
• Enable pre-emptive sandboxing for attachments from unknown senders

Step 3: Configure Impersonation Protect

• Create Default Impersonation Protect Definition (Hit 3) for all inbound email
• Create VIP Impersonation Protect Definition (Hit 1) for executive protection
• Build VIP list: CEO, CFO, CTO, board members, finance leadership
• Configure detection identifiers: display name, domain similarity, newly observed sender
• Set actions: quarantine high-confidence impersonation, tag moderate confidence
• Enable end-user warning banners for flagged messages

Step 4: Enable Internal Email Protect

• Configure journaling from Microsoft 365/Google Workspace to Mimecast
• Enable URL scanning for internal emails
• Enable attachment scanning for internal emails
• Configure alerts for internal account compromise indicators
• Set up detection for internal phishing (compromised account sending malware)

Step 5: Create Test Group and Validate

• Create pilot group of 50-100 users across departments
• Apply TTP policies to pilot group first
• Send test emails with known-safe test URLs and EICAR test files
• Verify URL rewriting, attachment sandboxing, and impersonation detection
• Monitor false positive rate for 1-2 weeks before organization-wide deployment

Step 6: Deploy Organization-Wide and Tune

• Extend TTP policies to all users
• Monitor Mimecast Threat Dashboard for detection metrics
• Review and whitelist legitimate applications triggering false positives
• Tune impersonation sensitivity based on false positive feedback
• Configure exception policies for automated systems and mailing lists

When NOT to Use

• You need to test the implementation (use performing-* skills)
• Task is about configuring existing tools (use configuring-* skills)
• You need to analyze security events (use analyzing-* skills)
• Task is about building detection rules (use building-* skills)
• You don't have access to the target environment
• Task requires vendor-specific expertise (consult vendor docs)

Red Flags

• Performing actions without explicit written authorization from the asset owner
• Testing against production systems without a defined scope and rules of engagement
• Exceeding the authorized scope of the engagement
• Leaving persistent access mechanisms without explicit approval
• Causing denial-of-service on production systems during testing

Verification

• All steps executed successfully against a test environment before production use
• Output documented with screenshots or logs demonstrating expected behavior
• All exploited vulnerabilities documented with reproduction steps
• Scope boundaries confirmed — only authorized targets were tested
• Remediation recommendations included for every finding

Tools & Resources

• Mimecast Administration Console: Policy configuration and management
• Mimecast Threat Dashboard: Real-time threat visibility and analytics
• Mimecast Awareness Training: Integrated security awareness platform
• Mimecast API: Programmatic access to logs and threat data
• Message Center: Quarantine management for admins and users

Validation

• URL Protect rewrites URLs in test messages and blocks known-malicious at click
• Attachment Protect sandboxes test file and returns verdict within SLA
• Impersonation Protect flags test BEC email impersonating VIP
• Internal Email Protect detects test lateral phishing scenario
• Pre-delivery hold catches weaponized URL before reaching inbox
• False positive rate below organizational threshold after tuning

Process

1. Analyze the task requirements
2. Apply domain expertise
3. Verify output quality

Anti-Rationalization Table