Email Authentication Attacks

Email authentication attacks exploit weaknesses in email authentication mechanisms to send spoofed emails that appear to come from legitimate domains.

This section covers various techniques for bypassing email authentication mechanisms such as SPF, DKIM, and DMARC, as well as other email spoofing techniques.

Email Authentication Overview

Email authentication mechanisms are designed to prevent email spoofing and phishing attacks by verifying that emails come from legitimate sources. The three main email authentication mechanisms are:

SPF (Sender Policy Framework): Verifies that the sending server is authorized to send email for the domain in the From header
DKIM (DomainKeys Identified Mail): Verifies that the email was cryptographically signed by the domain in the From header
DMARC (Domain-based Message Authentication, Reporting, and Conformance): Verifies that the email passes SPF and/or DKIM checks and that the From header domain aligns with the authenticated domain

Despite these mechanisms, there are various techniques that attackers can use to bypass email authentication and send spoofed emails.

DKIM Bypass

Techniques for bypassing DKIM email authentication

This attack focuses on bypassing DomainKeys Identified Mail (DKIM) email authentication to send spoofed emails that appear to come from a legitimate domain.

Learn More

SPF Bypass

Techniques for bypassing SPF email authentication

This attack focuses on bypassing Sender Policy Framework (SPF) email authentication to send spoofed emails that appear to come from a legitimate domain.

Learn More

Header Manipulation

Exploiting email header manipulation techniques

This attack involves manipulating email headers to bypass authentication mechanisms and create convincing spoofed emails.

Learn More

Authentication Results Injection

Exploiting Authentication-Results headers in email

This attack involves injecting fake Authentication-Results headers into emails to make them appear to have passed authentication checks when they haven't.

Learn More

Parsing Inconsistencies

Exploiting email parsing inconsistencies

This attack exploits inconsistencies in how different email systems parse and interpret email headers and content, allowing attackers to craft emails that appear differently to different systems.

Learn More

Service Account Spoofing

Exploiting service accounts for email spoofing

This attack exploits legitimate service accounts or third-party services that are authorized to send emails on behalf of a domain.

Learn More

Replay & Multiple From

Exploiting email replay and multiple From headers

This attack combines email replay techniques with multiple From headers to create sophisticated spoofing attacks that can bypass authentication mechanisms.

Learn More

General Mitigation Strategies

To protect against email authentication attacks, organizations should implement a comprehensive email security strategy that includes:

Implement all three authentication mechanisms: Use SPF, DKIM, and DMARC together for maximum protection
Use strict policies: Configure SPF and DMARC with strict policies (e.g., -all for SPF, p=reject for DMARC)
Monitor authentication failures: Use DMARC reporting to monitor authentication failures and adjust policies accordingly
Train users: Educate users about the risks of email spoofing and phishing
Use email security solutions: Implement email security solutions that can detect and block spoofed emails
Regularly audit configurations: Regularly audit SPF, DKIM, and DMARC configurations for weaknesses
Stay informed: Stay informed about new email authentication attacks and mitigation strategies

Back to Home View Methodology