Adversaries may fake, or spoof, a sender’s identity by modifying the value of relevant email headers in order to establish contact with victims under false pretenses.[1] In addition to actual email content, email headers (such as the FROM header, which contains the email address of the sender) may also be modified. Email clients display these headers when emails appear in a victim's inbox, which may cause modified emails to appear as if they were from the spoofed entity.
This behavior may succeed when the spoofed entity either does not enable or enforce identity authentication tools such as Sender Policy Framework (SPF), DomainKeys Identified Mail (DKIM), and/or Domain-based Message Authentication, Reporting and Conformance (DMARC).[2][3][4] Even if SPF and DKIM are configured properly, spoofing may still succeed when a domain sets a weak DMARC policy such as v=DMARC1; p=none; fo=1;. This means that while DMARC is technically present, email servers are not instructed to take any filtering action when emails fail authentication checks.[1][5]
Adversaries may abuse absent or weakly configured SPF, SKIM, and/or DMARC policies to conceal social engineering attempts[5] such as Phishing. They may also leverage email spoofing for Impersonation of legitimate external individuals and organizations, such as journalists and academics.[5]
| ID | Mitigation | Description |
|---|---|---|
| M1054 | Software Configuration |
Use anti-spoofing and email authentication mechanisms to filter messages based on validity checks of the sender domain (using SPF) and integrity of messages (using DKIM). Enabling these mechanisms within an organization (through policies such as DMARC) may enable recipients (intra-org and cross domain) to perform similar message filtering and validation.[6][7] |
| ID | Data Source | Data Component | Detects |
|---|---|---|---|
| DS0015 | Application Log | Application Log Content |
Monitor for third-party application logging, messaging, and/or other artifacts that may send phishing messages to gain access to victim systems. Filtering based on DKIM+SPF or header analysis can help detect when the email sender is spoofed.[6][7] Analytic 1 - Detect Spoofed Emails Using SPF/DKIM/DMARC Failures
Analytic 2 - Domain Mismatch Detection (Generic SMTP/Proxy Logs)
|