What is DMARC Vulnerability?by@powerdmarc
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What is DMARC Vulnerability?

by PowerDMARCMarch 1st, 2022
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DMARC vulnerability refers to common errors that users make while implementing the protocol or enforcing it. Vulnerabilities in your email authentication system can range from simple errors like wrong syntax to more complex errors. If not fixed, these vulnerabilities may cause problems in message deliverability and provide little to no protection against domain spoofing or phishing attacks. Using DMARC monitoring tools can help validate your DNS records from time to time to resolve DMARC vulnerabilities in real-time.

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DMARC records when configured in the right way can benefit you in more ways than one. It is a new realm in email security that offers domain owners a wealth of information about their email sending sources and performance. DMARC vulnerability refers to very common errors that users make while implementing the protocol or enforcing it.

Vulnerabilities in your email authentication system can range from simple errors like wrong syntax to more complex errors. Either way, unless you troubleshoot these issues and set up your protocol correctly, it may invalidate your email security efforts.

Before we analyze the possible vulnerabilities that you may encounter on your email authentication journey, let’s do a quick run-through of a few basic concepts. They are:

  1. What is email authentication?
  2. How does DMARC authenticate your emails?
  3. The impact of DMARC vulnerabilities on your message deliverability

What is Email Authentication?

Cybercriminals can extract financial benefits by intercepting email communications or using social engineering to defraud unsuspecting victims.

Email authentication refers to specific verification systems domain owners can configure to establish the legitimacy of emails sent from their domain. This can be done with the help of digital signatures placed in the message body, verification of Return-path addresses, and/or identifier alignment.

Once the authentication checks confirm the legitimacy of the message, the email gets dropped into the receiver’s inbox.

How does DMARC authenticate your emails?

When a company sends a message to its users, the email travels from the sending server to the receiving server to complete its deliverability journey. This email has a Mail From: header which is the visible header displaying the email address the email has been sent from and a Return-path header which is a hidden header containing the Return-path address.

An attacker can spoof the company domain to send emails from the same domain name, however, it is much more difficult for them to mask the Return-path address.

Let’s take a look at this suspicious email:

While the email address associated with the message seems to be coming from [email protected] which feels genuine, on inspecting the Return-path address it can be quickly established that the bounce address is completely unrelated to and was sent from an unknown domain.

This bounce address (aka Return-path address) is used by email receiving servers to look up a sender’s SPF record while verifying DMARC. If the sender’s DNS contains the IP address that matches the IP of the sent email, SPF and subsequently DMARC passes for it, else it fails. Now according to the DMARC policy configured by the sending domain, the message may get rejected, quarantined, or delivered.

Alternatively, DMARC may also check for DKIM identifier alignment to verify an email’s authenticity.

The impact of DMARC vulnerabilities on your message deliverability

The probability of your messages being delivered to your clients is hugely dependent on how accurately you have configured your protocol. Existing vulnerabilities in your organization’s email security posture can weaken the chances of your messages being delivered.

Certain clear indications of loopholes in your DMARC authentication system are as follows:

  1. Problems in email deliverability
  2. Increased susceptibility to email phishing and spoofing attacks
  3. Legitimate messages being marked as spam
  4. DMARC error prompts while using online tools

Types of DMARC Vulnerabilities

DMARC vulnerability #1: Syntactical errors in DNS records

A DMARC record is a TXT record with mechanisms separated by semicolons that specify certain instructions to email receiving MTAs. Given below is an example:

v=DMARC1; p=reject; rua=mailto:[email protected]; pct=100;

Small details such as the mechanism separators (;) play an important role in determining if your record is valid, and thus, cannot be overlooked. This is why to do away with the guesswork, we recommend that you use our free DMARC record generator tool to create an accurate TXT record for your domain.

DMARC vulnerability #2: No DMARC record found / DMARC record missing vulnerability

Domain owners may often come across a message while using online tools, prompting that their domain is missing a DMARC record. This can occur if you don’t have a valid record published on your DNS.

DMARC helps you protect your domain and organization against a wide range of attacks including phishing and direct domain spoofing. Living in a digital world with threat actors trying to intercept email communications every step of the way, we need to exercise caution and implement preventive measures to stop these attacks. DMARC aids in that process to promote a safer email environment.

To fix this, you need to access your DNS and create a TXT record for DMARC starting with v=DMARC1. Don’t forget to define a policy (reject/quarantine/none) for your emails!

DMARC vulnerability #3: Policy at none: monitoring only

A frequent misapprehension among users is that a DMARC policy at p=none is enough to protect their domain against attacks. In reality, only an enforced policy of reject/quarantine can help you build up your defenses against spoofing.

A relaxed policy can however be fruitful if you only want to monitor your email channels, without enforcing protection. It is however recommended that you make a quick shift to p=reject once you are confident.

We have placed this under the DMARC vulnerability category based on the criterion that most users implement DMARC to gain a higher degree of protection against attacks. Therefore, a policy with zero enforcement can be of no value to them.

DMARC vulnerability #4: DMARC policy not enabled

Similar to the previous vulnerability, this error prompt can often be a result of the lack of an enforced policy for DMARC. If you have set up your domain with a none policy, making it vulnerable to phishing attacks, it is a recommended practice to shift to p=reject/quarantine as soon as possible. To do so, you need only make a small tweak to your existing DNS record to modify and upgrade your policy mode.

Previous record (example): v=DMARC1; p=none; rua=mailto:[email protected]; pct=100;

Modified record (example): v=DMARC1; p=quarantine; rua=mailto:[email protected]; pct=100;

Troubleshooting DMARC vulnerabilities in real-time

To fix these issues you can consider implementing the following steps at your organization:

  • Make a list of all your authorized email sending sources and configure a DMARC monitoring tool to track them daily or from time to time

  • Have a discussion with your email vendors to substantiate whether they support email authentication practices

  • Learn about SPF, DKIM, and DMARC in detail before you move on to the next steps.

  • Make sure your SPF record is devoid of SPF Permerror by implementing an SPF flattening tool

  • Make your protocol implementation process seamless with expert insights and guidance from DMARC specialists. This can help you shift to p=reject safely with real-time vulnerability and attack detection.

    Protecting your domain is one of the primitive steps towards preserving your reputation and upholding your credibility. Make email security a part of your organization’s security posture today!