Create attachment_ics_excessive_self_reply_sender.yml

detection-rules/attachment_ics_excessive_self_reply_sender.yml

@@ -0,0 +1,42 @@
+name: "Attachment: Calendar invite from excessive self-reply sender"
+description: "Detect messages where there are 2 or more previous threads, where all previous messages are self-replies from the same sender, a calendar invite attachment with no physical location or generic online-meeting location, and B2B Cold Outreach topic analysis. This pattern is observed as excessive unsolicited outreach with disruptive required intervention."
+type: "rule"
+severity: "low"
+source: |
+  type.inbound
+  // previous threads are legitimate but are all self replies
+  and (
+    length(body.previous_threads) >= 2
+    and all(body.previous_threads, .sender.email.email == sender.email.email)
+  )
+
+  // calendar invite
+  and (
+    length(attachments) > 0
+    and all(attachments,
+            .content_type in ("text/calendar", "application/ics")
+            and any(file.explode(.),
+                    any(.scan.ics.calendars,
+                        any(.components,
+                            .location == null
+                            or strings.ilike(.location, "*online*")
+                        )
+                    )
+            )
+    )
+  )
+
+  // nlu logic
+  and any(ml.nlu_classifier(body.current_thread.text).topics,
+          .name == 'B2B Cold Outreach'
+  )
+attack_types:
+  - "Spam"
+tactics_and_techniques:
+  - "Social engineering"
+detection_methods:
+  - "Natural Language Understanding"
+  - "File analysis"
+  - "Header analysis"
+  - "Content analysis"
+id: "5a9ba97f-715e-5999-84d3-b459c1eb4117"