Detection Method: Header analysis

Header analysis inspects the metadata in message headers to find suspicious patterns, anomalies, or inconsistencies that could indicate phishing, spoofing, or other types of malicious activity. It looks at various header fields like routing information, authentication results, and sender verification data to help spot potential threats.
This includes sender authentication headers like SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting, and Conformance) results to verify the sender's legitimacy. It also checks how the email traveled through mail servers, looking for any unusual routing that might suggest tampering.
Header analysis can detect:
  • Email spoofing, where attackers forge the sender’s address to appear legitimate
  • Mismatched or inconsistent sender details
  • Suspicious return paths that don’t match the expected sender
  • Unusual routing patterns that stand out from normal email flow
  • Authentication failures that signal potential impersonation attempts
For example, attackers might try to forge email headers to make phishing emails appear as if they’re coming from a trusted source like your bank or your company’s internal email. Header analysis helps you catch these attempts by identifying mismatches between the displayed sender and the actual sending server.
Rule Name & Severity
Last Updated
Author
Types, Tactics & Capabilities
Brand Impersonation: Disney
17h ago
Mar 4th, 2026
Sublime Security
/feeds/core/detection-rules/brand-impersonation-disney-bf90b8fb
Service abuse: DocSend share from an unsolicited reply-to address
19h ago
Mar 4th, 2026
Sublime Security
/feeds/core/detection-rules/service-abuse-docsend-share-from-an-unsolicited-reply-to-address-b377e64c
BEC with unusual reply-to or return-path mismatch
2d ago
Mar 3rd, 2026
Sublime Security
/feeds/core/detection-rules/bec-with-unusual-reply-to-or-return-path-mismatch-83e5e2df
Brand impersonation: Chase Bank
3d ago
Mar 2nd, 2026
Sublime Security
/feeds/core/detection-rules/brand-impersonation-chase-bank-c680f1e7
VIP impersonation with w2 request with reply-to mismatch
6d ago
Feb 27th, 2026
Sublime Security
/feeds/core/detection-rules/vip-impersonation-with-w2-request-with-reply-to-mismatch-e7e73fad
Link: SharePoint OneNote or PDF link with self sender behavior
6d ago
Feb 27th, 2026
Sublime Security
/feeds/core/detection-rules/link-sharepoint-onenote-or-pdf-link-with-self-sender-behavior-588e7203
Headers: risky-recover-production message ID
7d ago
Feb 26th, 2026
Sublime Security
/feeds/core/detection-rules/headers-risky-recover-production-message-id-4cc0b5dc
Reconnaissance: Empty message from uncommon sender
8d ago
Feb 25th, 2026
Sublime Security
/feeds/core/detection-rules/reconnaissance-empty-message-from-uncommon-sender-b347cdbc
VIP / Executive impersonation (strict match, untrusted)
8d ago
Feb 25th, 2026
Sublime Security
/feeds/core/detection-rules/vip-executive-impersonation-strict-match-untrusted-e42c84b7
Brand impersonation: DocuSign
9d ago
Feb 24th, 2026
Sublime Security
/feeds/core/detection-rules/brand-impersonation-docusign-4d29235c
Spam: Sendersrv.com with financial communications and unsubscribe language
9d ago
Feb 24th, 2026
Sublime Security
/feeds/core/detection-rules/spam-sendersrvcom-with-financial-communications-and-unsubscribe-language-69570820
Link: Free file hosting with undisclosed recipients
10d ago
Feb 23rd, 2026
Sublime Security
/feeds/core/detection-rules/link-free-file-hosting-with-undisclosed-recipients-b6281306
Brand impersonation: Meta and subsidiaries
10d ago
Feb 23rd, 2026
Sublime Security
/feeds/core/detection-rules/brand-impersonation-meta-and-subsidiaries-e38f1e3b
Tax Form: W-8BEN solicitation
10d ago
Feb 23rd, 2026
Sublime Security
/feeds/core/detection-rules/tax-form-w-8ben-solicitation-a64edb69
Reconnaissance: Email address harvesting attempt
10d ago
Feb 23rd, 2026
Sublime Security
/feeds/core/detection-rules/reconnaissance-email-address-harvesting-attempt-bb31efbc
Brand impersonation: Survey request with credential theft indicators
13d ago
Feb 20th, 2026
Sublime Security
/feeds/core/detection-rules/brand-impersonation-survey-request-with-credential-theft-indicators-ea1c0e09
Cloud storage impersonation with credential theft indicators
13d ago
Feb 20th, 2026
Sublime Security
/feeds/core/detection-rules/cloud-storage-impersonation-with-credential-theft-indicators-4c20f72c
Brand impersonation: Gusto
15d ago
Feb 18th, 2026
Sublime Security
/feeds/core/detection-rules/brand-impersonation-gusto-54025c1c
Brand impersonation: American Express (AMEX)
16d ago
Feb 17th, 2026
Sublime Security
/feeds/core/detection-rules/brand-impersonation-american-express-amex-992a9fa9
File sharing link with a suspicious subject
16d ago
Feb 17th, 2026
Sublime Security
/feeds/core/detection-rules/file-sharing-link-with-a-suspicious-subject-a306e2a6