What is DMARC? DMARC Records and Their Role in Cybersecurity

In the current digital landscape, email security has become ever more important as cybercriminals frequently exploit vulnerabilities in email architectures to launch phishing attacks, steal sensitive information, and spoof legitimate domains. Since 2012, DMARC has become a cornerstone of modern email security, reducing the cyberattacks that occur via phishing and spoofing attacks in the process.

DMARC is a security protocol that allows domain owners to specify how unauthorized emails should be handled and verifies whether emails claiming to originate from a domain are actually authorized by the domain owner. Through its authentication and reporting features, DMARC affords domain owners greater control over their email communications, improves email deliverability, and enhances trust with email service providers and recipients.

What Does DMARC Stand For?

Developed in 2012, DMARC is short for Domain-based Message Authentication, Reporting, and Conformance. It is an email authentication method used to stop bad actors from impersonating an organization via email spoofing and phishing. Specifically, the components of DMARC function in the following way:

• Domain-based Message Authentication: DMARC leverages existing email protocols - SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) to ensure incoming emails originate from authorized senders and have not been tampered with.
• Reporting: DMARC offers detailed reports about authentication results from email testing. Hence, organizations are able to review the results to identify whether unauthorized senders are using their domain to send unsolicited emails or spam, thereby improving email security.
• Conformance: DMARC ensures conformance in email protocols by defining policies for handling unauthorized emails. This feature allows domain owners to specify how unauthenticated emails should be handled, such as quarantining, rejecting, or permitting them based on the security requirements defined by the organization.

Why is DMARC Important?

Although email remains one of the oldest forms of online communication, the authentication methods used in the process continue to evolve. Before the development of DMARC in 2012, email providers like Google relied heavily on strict filters and user feedback to identify and block spam. While effective in many instances, the filters used were overly stringent, sometimes preventing legitimate senders and domains from reaching their intended recipients.

DMARC brought a significant shift to email security, allowing senders to analyze detailed feedback reports and develop stringent authentication rules that specify which IP addresses are allowed to send emails on their behalf. Without DMARC, cybercriminals could easily forge emails to appear as though they were originating from a trusted source, thus tricking recipients into sharing sensitive information or clicking on malicious links. With a DMARC policy in place, Internet Service Providers (ISPs) can be instructed to reject emails coming from unauthorized or fraudulent IPs attempting to use a domain.

Hence, DMARC is able to play an important role in protecting individuals and organizations from a wide range of email-based threats, such as in the:

• Prevention of Phishing Attacks: DMARC helps to stop phishing attempts by ensuring that emails claiming to be from a specific domain are actually authorized by the domain owner. This prevents attackers from impersonating trusted entities, such as banks or businesses, to trick recipients into revealing sensitive information.
• Protection Against Email Spoofing: Spoofing usually involves forging the sender’s email address to make it appear as though the message is from a legitimate source. With DMARC, an organization is able to authenticate incoming emails by verifying them against SPF and DKIM protocols. This ensures that only authorized senders can use the domain.
• Improved Email Deliverability: By implementing DMARC, organizations demonstrate to email providers that their messages are secure and legitimate. This improves the reputation of their domain, reducing the likelihood of legitimate emails being flagged as spam.

What is a DMARC Record?

A DMARC record is a Domain Name System (DNS) entry storing a domain’s DMARC policy. It is stored as a DNS TXT record and contains instructions on how an organization's email server should handle emails that fail authentication. Hence, via the DMARC record, an organization may control whether email receivers should quarantine, reject, or do nothing with a suspicious email. These sets of instructions are called the DMARC policy.

Creating DMARC records is important as it helps email services separate between fake emails and legitimate ones. Consequently, an organization is able to minimize attacks like email spoofing, phishing, and CEO fraud. DMARC functions by integrating with two existing authentication protocols, SPF and DKIM, to ensure emails are sent from authorized servers and that email contents have not been tampered with during transmission.

Structure of a DMARC Record

Typically, DMARC records contain three components:

• Policy: The policy (p) is the core directive in the record, and it determines how email authentication will be handled. The policy is usually set to one of the following:
  • p=none: No action is taken; only reports are collected. Unauthenticated emails are delivered.
  • p=quarantine: Suspicious emails are sent to the spam or junk folder.
  • p=reject: Unauthenticated emails are blocked entirely and do not get delivered to the recipients.
• Alignment: This component verifies whether the domain in the "From" address matches with the domains used in the SPF and DKIM authentication checks. The two alignment modes in a DMARC record are:
  • Strict alignment: This requires that domains must match exactly.
  • Relaxed alignment: This allows slight variations between domains. Subdomains are allowed.
• Reporting: The reporting component ensures that domain owners are provided with detailed information and data about email authentication. This is commonly set to either of the following:
  • Aggregate Reports (rua=): This provides summarized data about email authentication results and is sent periodically.
  • Forensic Reports (ruf=): Detailed reports about specific emails that failed authentication.

How To Create and Set Up a DMARC Record

To set up a DMARC record on your domain, you may follow these steps:

• Review your current email configuration setup: Before you may implement DMARC on your domain, you need to ensure that you have SPF and DKIM both operational. These two protocols are required for DMARC to function effectively.
• Decide on the components you want in your DMARC record: Select the DMARC policy, alignment, and reporting values that best fit your needs.
• Prepare the DMARC TXT record: The  DMARC record is a TXT record added to your domain’s DNS settings. It follows this example: v=DMARC1; p=none; rua=mailto:reports@yourtruedomain.com; ruf=mailto:forensic@yourtruedomain.com; adkim=s; aspf=r;

These indicate:

v=DMARC1: Specifies the DMARC version.

p=none/quarantine/reject: Defines the policy for handling unauthorized emails.

rua=:The email address to receive aggregate reports.

ruf=: The email address to receive forensic reports.

adkim=s: Alignment mode for DKIM is strict

aspf=r: Alignment mode for SPF is relaxed

• Add the DMARC record to your DNS: Log into your DNS provider's control panel and navigate to the DNS management section to locate the option to add a TXT record. Add the new TXT record with:

Host: _dmarc.yourdomain.com

Value: Your DMARC policy string.

TTL: Default (for example, 1 hour)

Save and apply the changes

• Monitor and adjust the policy: Once the DMARC record is live, monitor the reports generated by the protocol. Afterward, you should analyze reports for insights into email authentication and unauthorized activities. Over time, you may gradually move from a none policy to quarantine or reject for stronger protection.

DMARC's Role in Cybersecurity

DMARC's role in cybersecurity cannot be underplayed as it plays an important part in protecting domains from malicious email activities, including spoofing and phishing attacks. By enforcing authentication protocols, DMARC ensures that only legitimate emails are sent from a domain, reducing the risk of fraud and improving email deliverability.

How DMARC Prevents Phishing and Spoofing

Although phishing and spoofing are some of the most common email-based threats, deploying DMARC can ensure a significant reduction in the number of such threats. According to a report published by Verizon's Data Breach Investigations, organizations that have adopted DMARC have witnessed about a 20% reduction in phishing incidents. DMARC can reduce phishing and spoofing threats in the following ways:

• Domain Authentication: DMARC ensures that only authorized senders can send emails on behalf of a domain. By verifying the alignment of the "From" address with the domain used in SPF and DKIM checks, DMARC prevents attackers from impersonating legitimate entities.
• Policy Enforcement: Domain owners can specify how unauthenticated emails should be handled, whether they should be monitored, quarantined, or rejected. This enforcement mechanism significantly reduces the likelihood of fraudulent emails reaching recipients.

The Relationship Between DMARC and Other Email Authentication Protocol.

DMARC needs SPF and DKIM to function as it is built on these two key email authentication protocols. Sender Policy Framework (SPF) works by verifying that emails come from authorized mail servers by checking the sender's IP address against a list of approved senders. DMARC leverages this protocol to ensure that the sender's domain matches the domain specified in the "From" header.

DKIM uses cryptographic signatures to confirm that an email has not been altered during transit and that it originates from a verified source. DMARC aligns the domain in the DKIM signature with the "From" address to ascertain authenticity.

DMARC combines SPF and DKIM by instructing receiving mail servers on how to handle emails that fail authentication checks. If an email does not pass SPF and DKIM, DMARC can reject it outright, reducing the risk of email-based cyber threats.

Benefits of DMARC for Organizations

Implementing DMARC comes with several advantages that organizations may benefit from. Some of these benefits include ensuring the protection of brand reputation, improved email security, and better control over email communication. 

These benefits are possible since DMARC verifies that emails are genuinely sent from an organization's authorized sources, thereby reducing the risk of malicious actors. Also, DMARC allows organizations the ability to set policies for handling unauthenticated emails, whether to allow monitoring, quarantining suspicious emails, or outright rejecting fraudulent ones. These benefits allow organizations greater control over email communications.

Enhancing Email Trustworthiness

Email trustworthiness is a big hurdle in email communications. Implementing DMARC allows an organization to improve the legitimacy of its emails in the eyes of recipients and email service providers. First, DMARC is able to help an organization boost email recipients' confidence as customers receive emails from a domain protected by the authentication method, they are able to trust that the messages are authentic. This reduces the chances of ignoring or flagging legitimate communications as spam.

In addition, DMARC strengthens a domain's reputation with email service providers like Gmail, Yahoo, and Outlook. Authenticated emails are less likely to be marked as spam, resulting in higher deliverability rates and better engagement with recipients.

Challenges and Considerations in Implementing DMARC

Configuring and setting up DMARC may throw up certain challenges that must be addressed to ensure a smoother setup process and effective protection for email authentication. Some of these challenges include: 

• Legacy Systems: Some organizations use older email infrastructure, which may not fully support SPD, DKIM, or DMARC. In such cases, implementing DMARC may be more challenging than it would normally be. To solve this problem, organizations should look to upgrading their current systems or using third-party services to help bridge compatibility gaps.
• Resource Requirements: Configuring and implementing DMARC requires technical expertise and ongoing resources for monitoring and managing reports. To mitigate this, an organization may consult with email security experts or use DMARC automation tools to simplify the process
• Complexity of Implementation: Since DMARC requires collaboration with existing protocols, such as DKIM and SPF, organizations that do not have the necessary prior experience in email authentication may find this challenging. Organizations in this category should consider starting with a "none" policy to monitor email activity and gradually move to stricter policies like quarantine or reject.
• Deliverability Concerns: If DMARC is poorly configured, the chances are high that it would lead to legitimate emails being marked as spam or rejected. To avoid this, organizations should conduct thorough testing and use DMARC reports to identify and resolve issues during the rollout phase.

Common DMARC Configuration Errors

Mistakes may occur during the implementation stage for DMARC. Some common DMARC configuration errors are: 

• SPF or DKIM Misalignment: DMARC requires the SPF or DKIM to align with the "From" domain. If the domains in both protocols do not align with the "From" header, emails may fail authentication.
• Misconfigured Policies: Legitimate emails may be blocked if the policies in the DMARC are not properly set. For instance, setting a policy to "reject" too soon without proper monitoring may cause this. Organizations are advised to start with a "none" policy to collect reports and monitor email traffic before enforcing stricter policies.
• Incomplete DNS TXT Records: An incorrectly formatted or missing DMARC record in the DNS setting will prevent the configuration from functioning properly. Double-checking the syntax of the record and using validation tools can help ensure the accuracy of the record.
• Ignoring DMARC Reports: Many organizations fail to monitor or act on DMARC reports, missing valuable insights into unauthorized activity. Organizations should regularly review these reports to identify patterns, detect abuse, and refine policies as needed.
• Overly Broad SPF Records: SPF records exceeding the 10 DNS lookup limit may cause validation failures. Using SPF flattening or consolidating SPF entries may help prevent issues.
• Forgetting Subdomains: By default, DMARC applies only to the main domain, leaving subdomains vulnerable. However, organizations may use the "sp" tag in the DMARC record to define policies for subdomains.
• Failure to Test Before Deployment: Rolling out a DMARC policy without proper testing may disrupt legitimate email traffic. Organizations should use DMARC testing tools and deploy them gradually, adjusting policies based on reports.