So simple but obviously unknown! 
The use of DKIM and DMARC 
to protect against cyberattacks 
through malicious mails

A link for your self-check is listed at the end of this article. 

One of the most common attack vectors is the dissemination of malicious mail that uses phishing, spoofing, or malware to gain access to confidential information or control over systems. To effectively counter this threat scenario, technologies such as DKIM (DomainKeys Identified Mail) and DMARC (Domain-based Message Authentication, Reporting, and Conformance) are critical.

DKIM is a security mechanism that verifies the authenticity of emails by generating digital signatures for outgoing emails. These signatures are based on asymmetric cryptography and are signed with the domain's public key. The recipient can verify the signature to ensure that the email is unaltered during transport and originates from the specified domain. In this way, forged sender addresses and data manipulation can be detected and prevented.

DMARC, on the other hand, is a mechanism to combat email fraud by validating the implementation of SPF (Sender Policy Framework) and DKIM. It allows the sender to set policies that define how emails with spoofed senders should be handled. DMARC helps reduce spoofing attacks by ensuring that emails are sent only from authorized sources and that spoofed emails are blocked or moved to the spam folder.

Together, DKIM and DMARC form a powerful duo in the fight against malicious email. They offer several advantages in protecting against cyberattacks:

  1. Authentication of senders
    DKIM ensures that emails come from truly authorized senders by verifying digital signatures. This helps to detect and block spoofed sender addresses.

  2. Integrity check
    DKIM ensures that email content remains unchanged in transit by checking the integrity of the message. This is critical to prevent tampering with email content.

  3. Combating phishing
    Phishing attacks aimed at deceiving recipients can be made significantly more difficult by using DKIM and DMARC. Verifying the authenticity of the sender helps detect and block fake websites or malicious links.

  4. Limiting spoofing
    DMARC helps minimize spoofing attacks by ensuring that emails originate only from verified servers with authorized signatures. This helps reduce fraudulent activity where attackers pretend to originate from legitimate organizations.

  5. Improving the corporate reputation
    By using DKIM and DMARC, companies demonstrate their responsibility in dealing with email security, which in turn strengthens the trust of their customers and partners.

Despite their effectiveness, DKIM and DMARC are not a standalone solution for mail security. A holistic cybersecurity strategy that includes other security measures such as firewalls, antivirus software and employee training is critical to ensure a comprehensive defense against cyberattacks.

Overall, DKIM and DMARC have become indispensable tools in any organization's arsenal to successfully counter growing malware threats. Their implementation helps make the digital landscape more secure by protecting the integrity and authenticity of emails, laying the foundation for trusted communications in today's digital era.

The procedure was developed by Yahoo under the name DomainKeys and submitted to the IETF for standardization back in 2007. This makes it all the more incomprehensible that we were only able to identify DKIM signatures in 177 companies out of 1450 in the automotive industry.  With this simple and easy procedure, the trust in mail communication between companies could be significantly improved.

Do your own check: provides a console for anyone interested, which uses visual breakdowns to provide a better understanding of SPF, DKIM and DMARC and how they interact.

[j]karef unterstützt Sie nicht nur dabei, Ihre IT Infrastruktur vor Cyber-Angriffen zu verbergen. Mit JOUO machen wir das Unsichtbare sichtbar und helfen Ihnen dabei, Ihre Angriffsfläche zu verringern.


Kontaktieren Sie mich für eine kostenlose Erstberatung:

Rüdiger Henrici, [email protected]
+49 (0) 30 555797650