Create fake_ooo_urgent_financial_request.yml

detection-rules/fake_ooo_urgent_financial_request.yml

@@ -0,0 +1,50 @@
+name: "Out-of-office auto-reply with urgent financial request from free email provider"
+description: "Detects suspicious out-of-office messages from free email providers that contain urgent financial payment requests. These messages combine legitimate auto-reply topics with BEC indicators including urgency, financial terms, and payment processing language to appear trustworthy while requesting financial actions."
+type: "rule"
+severity: "low"
+source: |
+  type.inbound
+  and sender.email.domain.root_domain in~ $free_email_providers
+  and length(body.previous_threads) == 0
+  and length(body.current_thread.text) < 500
+  and not subject.is_reply
+  and not subject.is_forward
+
+  // out-of-office topic
+  and any(ml.nlu_classifier(body.current_thread.text).topics,
+          .name == "Out of Office and Automatic Replies"
+  )
+  // urgent and financial entities
+  and (
+    (
+      any(ml.nlu_classifier(body.current_thread.text).entities,
+          .name == "urgency"
+      )
+      and any(ml.nlu_classifier(body.current_thread.text).entities,
+              .name == "financial"
+      )
+    )
+    // or high confidence in bec/cred_theft/callback_scam
+    or any(ml.nlu_classifier(body.current_thread.text).intents,
+           .name in ("bec", "cred_theft", "callback_scam")
+           and .confidence != "low"
+    )
+  )
+  and (
+    strings.icontains(body.current_thread.text, "handle the payment")
+    or strings.icontains(body.current_thread.text, "process the invoice")
+    or strings.icontains(body.current_thread.text, "expense payment")
+    or strings.icontains(body.current_thread.text, "payment during")
+  )
+attack_types:
+  - "BEC/Fraud"
+tactics_and_techniques:
+  - "Free email provider"
+  - "Impersonation: Employee"
+  - "Social engineering"
+detection_methods:
+  - "Content analysis"
+  - "Header analysis"
+  - "Natural Language Understanding"
+  - "Sender analysis"
+id: "5c9fc8ab-84d7-5bf3-a044-101529ef0d9a"