Introduction
Domain-based Message Authentication, Reporting, and Conformance (DMARC) is a powerful email authentication protocol designed to protect domains from email spoofing and phishing attacks. Beyond its role in preventing unauthorized email activity, DMARC also provides valuable reporting features that can be leveraged for threat intelligence and incident response.
By analyzing DMARC reports, organizations can gain insights into email authentication failures, detect malicious activity targeting their domain, and take proactive measures to secure their infrastructure. This article explores how to use DMARC reports effectively for threat intelligence and incident response.
What Are DMARC Reports?
DMARC generates two types of reports:
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Aggregate Reports (RUA): High-level reports providing data on email authentication results, including sending sources, IP addresses, and authentication pass/fail details
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Forensic Reports (RUF): More detailed reports, sent when a message fails DMARC, containing message headers and sometimes message bodies
These reports are sent to the email addresses specified in the DMARC record using the rua and ruf tags.
How DMARC Reports Support Threat Intelligence
1. Identifying Malicious Sending Sources
- DMARC aggregate reports list the IP addresses sending emails on behalf of your domain
- By comparing these IPs against known internal IP ranges and trusted third-party services, unauthorized sources can be identified
2. Detecting Spoofing Attempts
- A high rate of DMARC failures from specific IP addresses may indicate spoofing attempts
- Forensic reports can provide message samples to assess the content of these failed emails
3. Monitoring Third-Party Services
- DMARC data helps verify whether authorized third-party services (e.g., marketing platforms) are properly configured with SPF and DKIM alignment
4. Geolocation Analysis
- Threat actors often operate from specific regions
- DMARC data can be cross-referenced with IP geolocation databases to identify suspicious regions of origin
Steps to Leverage DMARC for Incident Response
Step 1: DMARC Record Setup
Ensure a proper DMARC record is published in your domain's DNS.
Example:
_dmarc.example.com TXT "v=DMARC1; p=quarantine; rua=mailto:dmarc-reports@example.com; ruf=mailto:forensic-reports@example.com"
p=quarantine: Emails failing DMARC are marked as suspiciousrua: Specifies where aggregate reports should be sentruf: Specifies where forensic reports should be sent
Step 2: Report Collection and Storage
- Use a DMARC reporting tool or service like YourDMARC to collect and store DMARC reports for easy analysis
- Maintain a secure, centralized repository for all collected reports
Step 3: Data Correlation and Analysis
- Correlate IP data: Compare sending IP addresses against threat intelligence feeds (e.g., AbuseIPDB, VirusTotal)
- Identify Patterns: Analyze patterns in failed authentication results over time
- Flag Unrecognized Sources: Cross-check IPs against your authorized email sources
Step 4: Incident Response Actions
When suspicious activity is identified:
- Quarantine or Reject: Adjust your DMARC policy from
p=nonetop=quarantineorp=reject - Block Malicious IPs: Implement firewall rules to block unauthorized senders
- Alert Security Teams: Share forensic reports with the incident response team for deeper investigation
- Update DNS Records: Ensure SPF and DKIM records are up to date and reflect authorized services
Automating Threat Intelligence with DMARC Tools
To streamline DMARC-based threat intelligence:
- DMARC Monitoring Services: Tools like YourDMARC provide automated report parsing and threat detection dashboards
- SIEM Integration: DMARC data can be fed into Security Information and Event Management (SIEM) platforms for correlation with other security events
Conclusion
Leveraging DMARC reports for threat intelligence and incident response can significantly enhance your organization's ability to detect and mitigate email threats. By implementing a robust DMARC policy and regularly reviewing reports, you can identify unauthorized email activity, monitor third-party services, and respond to incidents effectively.
At YourDMARC, we specialize in simplifying DMARC management and threat intelligence for businesses. Get started today to secure your email ecosystem and protect your brand against phishing and spoofing attacks.
