[Test Rules] [PR #4513] added rule: VIP impersonation with BEC language (near match, untrusted sender)

Author: github-actions[bot]

detection-rules/4513_impersonation_vip_bec_loose.yml

@@ -0,0 +1,68 @@
+name: "VIP impersonation with BEC language (near match, untrusted sender)"
+description: |
+  Sender is using a display name that matches the display name of someone in your $org_vips list.
+
+  Detects potential Business Email Compromise (BEC) attacks by analyzing text within email body from untrusted senders.
+type: "rule"
+severity: "medium"
+source: |
+  type.inbound
+  and any($org_vips,
+          0 <= strings.ilevenshtein(sender.display_name, .display_name) < 4
+          or 0 <= strings.ilevenshtein(sender.display_name,
+                                       strings.concat(.first_name,
+                                                      " ",
+                                                      .last_name
+                                       )
+          ) < 4
+          or 0 <= strings.ilevenshtein(sender.display_name,
+                                       strings.concat(.last_name,
+                                                      ", ",
+                                                      .first_name
+                                       )
+          ) < 4
+  )
+  and any(ml.nlu_classifier(body.current_thread.text).intents,
+          .name == "bec" and .confidence in ("medium", "high")
+  )
+  and (
+    (
+      profile.by_sender().prevalence != "common"
+      and not profile.by_sender().solicited
+    )
+    or (
+      profile.by_sender().any_messages_malicious_or_spam
+      and not profile.by_sender().any_messages_benign
+    )
+    or profile.by_sender().days_since.last_outbound > 365
+  )
+  // negate sharepoint notifications originating from within the org
+  and not (
+    sender.email.email in ('no-reply@sharepointonline.com')
+    and length(headers.reply_to) > 0
+    and all(headers.reply_to, .email.domain.root_domain in $org_domains)
+  )
+  // negate highly trusted sender domains unless they fail DMARC authentication
+  and (
+    (
+      sender.email.domain.root_domain in $high_trust_sender_root_domains
+      and not headers.auth_summary.dmarc.pass
+    )
+    or sender.email.domain.root_domain not in $high_trust_sender_root_domains
+  )
+  and not profile.by_sender().any_messages_benign
+tags:
+  - "Attack surface reduction"
+attack_types:
+  - "BEC/Fraud"
+tactics_and_techniques:
+  - "Impersonation: VIP"
+  - "Social engineering"
+detection_methods:
+  - "Content analysis"
+  - "Natural Language Understanding"
+  - "Sender analysis"
+id: "af52ee6e-31f3-52e7-ba94-1e460c89628f"
+og_id: "303081da-6850-5ba6-9589-c3dc7673320e"
+testing_pr: 4513
+testing_sha: 90a3176084fd25d367a7582d78b2cd7bb9c4b8b5