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: DocuSign
3d ago
Apr 17th, 2026
Sublime Security
BEC/Fraud: Urgent language and suspicious sending/infrastructure patterns
3d ago
Apr 17th, 2026
Sublime Security
Self-sender with copy/paste instructions and suspicious domains (French/Français)
4d ago
Apr 16th, 2026
Sublime Security
Brand impersonation: Amazon with suspicious attachment
6d ago
Apr 14th, 2026
Sublime Security
Advance Fee Fraud (AFF) from freemail provider or suspicious TLD
6d ago
Apr 14th, 2026
Sublime Security
Attachment: Compensation review lure with QR code
6d ago
Apr 14th, 2026
Sublime Security
Callback phishing via Microsoft comment
7d ago
Apr 13th, 2026
Sublime Security
Attachment: PDF with credential theft language and invalid reply-to domain
10d ago
Apr 10th, 2026
Sublime Security
Link: Shortened URL with fragment matching subject
11d ago
Apr 9th, 2026
Sublime Security
Brand impersonation: McAfee
11d ago
Apr 9th, 2026
Sublime Security
Cloud storage impersonation with credential theft indicators
11d ago
Apr 9th, 2026
Sublime Security
Service abuse: GitHub notification with excessive mentions and suspicious links
13d ago
Apr 7th, 2026
Sublime Security
QR Code with suspicious indicators
14d ago
Apr 6th, 2026
Sublime Security
VIP impersonation: Fake thread with display name match, email mismatch
17d ago
Apr 3rd, 2026
Sublime Security
Brand impersonation: Toronto-Dominion Bank
17d ago
Apr 3rd, 2026
Sublime Security
Attachment: Legal themed message or PDF with suspicious indicators
17d ago
Apr 3rd, 2026
Sublime Security
Benefits enrollment impersonation
17d ago
Apr 3rd, 2026
Sublime Security
Service abuse: Google Firebase sender address with suspicious content
18d ago
Apr 2nd, 2026
Sublime Security
Link: Personalized URL with recipient address on commonly abused web service
19d ago
Apr 1st, 2026
Sublime Security
Brand impersonation: Bank of America
20d ago
Mar 31st, 2026
Sublime Security