Detections
Explore public detection logic contributed by the community across SIEM and rule languages.
26 detections
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Detects inbound emails where the sender claims to be from an internal or organization domain but has a null envelope sender address, lacks valid DKIM authentication, and does not match common legitimate automated messages (like DSNs or auto-replies), potentially indicating email spoofing or phishing attempts.
Detects emails from free-mail domains (@mail.com or @outlook.com) that contain a specific malicious infrastructure indicator in the InternetMessageId or originate from a known suspicious IP address associated with TA419-style spoofing campaigns. This indicates the email was relayed through unauthorized infrastructure rather than the expected legitimate mail providers.
Detects emails from free-mail domains (@mail.com or @outlook.com) that contain a specific malicious infrastructure indicator in the InternetMessageId or originate from a known suspicious IP address associated with TA419-style spoofing campaigns. This indicates the email was relayed through unauthorized infrastructure rather than the expected legitimate mail providers.
Detects emails from free-mail domains (@mail.com or @outlook.com) that contain a specific malicious infrastructure indicator in the InternetMessageId or originate from a known suspicious IP address associated with TA419-style spoofing campaigns. This indicates the email was relayed through unauthorized infrastructure rather than the expected legitimate mail providers.
Detects emails from free-mail domains (@mail.com or @outlook.com) that contain a specific malicious infrastructure indicator in the InternetMessageId or originate from a known suspicious IP address associated with TA419-style spoofing campaigns. This indicates the email was relayed through unauthorized infrastructure rather than the expected legitimate mail providers.
Detects inbound emails that have been delivered to the user's Inbox or Junk folder despite failing SPF authentication checks. The detection logic triggers when these emails also lack a valid DMARC policy (none or not available), which prevents the mail server from enforcing rejection or quarantine, allowing spoofed or unauthenticated mail to bypass standard security filters.
Detects emails from free-mail domains (@mail.com or @outlook.com) that contain a specific malicious infrastructure indicator in the InternetMessageId or originate from a known suspicious IP address associated with TA419-style spoofing campaigns. This indicates the email was relayed through unauthorized infrastructure rather than the expected legitimate mail providers.
Detects inbound emails that have been delivered to the user's Inbox or Junk folder despite failing SPF authentication checks. The detection logic triggers when these emails also lack a valid DMARC policy (none or not available), which prevents the mail server from enforcing rejection or quarantine, allowing spoofed or unauthenticated mail to bypass standard security filters.
Detects downstream delivery of likely AI-paraphrased mass-produced lure content by identifying bursts of near-duplicate subject lines from newly-seen domains with auth failures.
Detects downstream delivery of likely AI-paraphrased mass-produced lure content by identifying bursts of near-duplicate subject lines from newly-seen domains with auth failures.
Detects downstream delivery of likely AI-paraphrased mass-produced lure content by identifying bursts of near-duplicate subject lines from newly-seen domains with auth failures.
Detects downstream delivery of likely AI-paraphrased mass-produced lure content by identifying bursts of near-duplicate subject lines from newly-seen domains with auth failures.
Audits Direct Send traffic against an approved-IP watchlist, flagging unauthenticated inbound mail spoofing an internal domain from an unrecognized source IP. Fixed: RecipientDomain/SenderFromDomain were referenced but never defined (would have errored at runtime); replaced with derived SenderDomain/RecipientDomain consistent with the sibling rules. Removed a noisy display-name-contains-domain OR-branch. Replaced an always-true-in-practice auth check (required every one of SPF/DKIM/DMARC to show literal "Pass", which fails for many legitimate senders that pass via alignment on only one protocol) with the same CompAuth/all-three-fail logic used elsewhere in this set.
Detects the RejectDirectSend bypass (null SMTP envelope sender + internal-domain spoof). Tightened to require Microsoft's composite auth verdict OR all of SPF/DKIM/DMARC failing (vs. any one), excludes known-approved Direct Send relay IPs, and excludes likely-legitimate bulk/newsletter traffic via BulkComplaintLevel.
Audits Direct Send traffic against an approved-IP watchlist, flagging unauthenticated inbound mail spoofing an internal domain from an unrecognized source IP. Fixed: RecipientDomain/SenderFromDomain were referenced but never defined (would have errored at runtime); replaced with derived SenderDomain/RecipientDomain consistent with the sibling rules. Removed a noisy display-name-contains-domain OR-branch. Replaced an always-true-in-practice auth check (required every one of SPF/DKIM/DMARC to show literal "Pass", which fails for many legitimate senders that pass via alignment on only one protocol) with the same CompAuth/all-three-fail logic used elsewhere in this set.
Detects the RejectDirectSend bypass (null SMTP envelope sender + internal-domain spoof). Tightened to require Microsoft's composite auth verdict OR all of SPF/DKIM/DMARC failing (vs. any one), excludes known-approved Direct Send relay IPs, and excludes likely-legitimate bulk/newsletter traffic via BulkComplaintLevel.
Detects incoming emails where the SMTP envelope sender (MAIL FROM) is blank, but the visible 'From' header displays an internal/accepted domain. This technique is often used to bypass email authentication filters. The rule specifically alerts on cases where SPF, DKIM, or DMARC checks failed or returned 'none', yet the message was still delivered to an inbox or folder, suggesting a configuration gap or allow-list override.
Detects the RejectDirectSend bypass (null SMTP envelope sender + internal-domain spoof). Tightened to require Microsoft's composite auth verdict OR all of SPF/DKIM/DMARC failing (vs. any one), excludes known-approved Direct Send relay IPs, and excludes likely-legitimate bulk/newsletter traffic via BulkComplaintLevel.
Detects the RejectDirectSend bypass (null SMTP envelope sender + internal-domain spoof). Tightened to require Microsoft's composite auth verdict OR all of SPF/DKIM/DMARC failing (vs. any one), excludes known-approved Direct Send relay IPs, and excludes likely-legitimate bulk/newsletter traffic via BulkComplaintLevel.
Detects incoming emails where the SMTP envelope sender (MAIL FROM) is blank, but the visible 'From' header displays an internal/accepted domain. This technique is often used to bypass email authentication filters. The rule specifically alerts on cases where SPF, DKIM, or DMARC checks failed or returned 'none', yet the message was still delivered to an inbox or folder, suggesting a configuration gap or allow-list override.
Audits Direct Send traffic against an approved-IP watchlist, flagging unauthenticated inbound mail spoofing an internal domain from an unrecognized source IP. Fixed: RecipientDomain/SenderFromDomain were referenced but never defined (would have errored at runtime); replaced with derived SenderDomain/RecipientDomain consistent with the sibling rules. Removed a noisy display-name-contains-domain OR-branch. Replaced an always-true-in-practice auth check (required every one of SPF/DKIM/DMARC to show literal "Pass", which fails for many legitimate senders that pass via alignment on only one protocol) with the same CompAuth/all-three-fail logic used elsewhere in this set.
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