DMARC

DMARC (Domain-based Message Authentication, Reporting & Conformance) is an email security protocol designed to help domain owners protect their users from fraudulent emails like phishing and spoofing. DMARC relies on two other email authentication mechanisms: SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail). The goal of DMARC is to improve email security by allowing senders to specify policies for handling emails that fail these authentication checks.

When DMARC is implemented, it allows domain owners to specify:

  • How receiving servers should handle emails that fail SPF or DKIM checks.
  • To receive reports on emails sent with their domain, helping them monitor abuse or fraud attempts.

In short, DMARC gives domain owners control over how their emails are handled by other servers and provides diagnostic feedback on how their domain is being used.

How DMARC Works

  1. SPF and DKIM Authentication:
    • DMARC relies on SPF and DKIM to verify that messages come from the legitimate sender. SPF checks that the sender’s IP is authorized to send emails for the given domain. DKIM verifies that the email has not been altered in transit and that the sender is legitimate.
  2. DMARC Policy:
    • The domain owner creates a DMARC record in the domain’s DNS. This record contains information on how to handle emails that fail authentication:
      • none: No specific action, only report collection.
      • quarantine: Emails that fail authentication are marked as suspicious (e.g., sent to the spam folder).
      • reject: Emails that fail authentication are outright rejected by the receiving server.
  3. DMARC Reports:
    • DMARC allows domain owners to receive aggregated and detailed reports on emails sent using their domain. These reports help monitor abuse, such as phishing or spoofing attempts, and adjust the policy as needed.

Advantages of DMARC

  1. Protection Against Phishing and Spoofing:
    • DMARC prevents attackers from spoofing your domain and sending fraudulent emails on behalf of your business or organization.
  2. Improved Legitimate Email Deliverability:
    • By using DMARC, you improve your domain’s reputation, increasing the likelihood that your legitimate emails land in the recipient’s inbox rather than the spam folder.
  3. Control and Visibility:
    • DMARC gives domain owners active control over their domain’s usage and alerts them to any suspicious activity. Detailed reports help identify sources of abuse.
  4. Complementary to SPF and DKIM:
    • DMARC works alongside SPF and DKIM to provide an additional layer of security, reinforcing email verification.

Limitations of DMARC

  1. Complex Setup:
    • Setting up DMARC correctly requires an understanding of SPF, DKIM, and how to manage DNS records. A misconfiguration can lead to legitimate emails being rejected.
  2. Dependency on SPF and DKIM:
    • DMARC can only be effective if SPF and DKIM are properly configured. If these two authentication mechanisms fail, DMARC cannot function optimally.
  3. Limited Reporting in Some Configurations:
    • DMARC reports can be difficult to interpret for non-technical users, and they may not provide enough detail to diagnose complex issues.

DMARC Implementation

  1. Creating the DMARC Record:
    • The domain administrator creates a DMARC record in the domain’s DNS, specifying the desired policy (none, quarantine, or reject) and the email address where reports should be sent.
  2. Setting Up SPF and DKIM:
    • Before using DMARC, SPF and DKIM must be properly configured. SPF specifies which servers are authorized to send emails for a domain, and DKIM ensures that the message has not been altered in transit.
  3. Analyzing Reports:
    • Once DMARC is set up, aggregated reports should be reviewed regularly to detect any fraud attempts or misuse and adjust the DMARC policy accordingly.

Conclusion

DMARC is a crucial email security protocol for protecting a domain from identity spoofing and phishing attacks. By combining DMARC with other email security technologies like SPF and DKIM, businesses can significantly reduce the risk of phishing and improve email deliverability. However, proper implementation requires careful management of cryptographic keys and DNS records.

Catégories d’articles