[PR #3058] changed rule: Cloud storage impersonation with credential theft indicators

Author: github-actions[bot]

detection-rules/3058_credential_theft_cloud_storage_impersonation.yml

@@ -0,0 +1,68 @@
+name: "Cloud storage impersonation with credential theft indicators"
+description: "Detects messages impersonating cloud storage services that contain hyperlinked images leading to free file hosts, where message screenshots reveal high-confidence credential theft language and storage-related urgency tactics."
+type: "rule"
+severity: "medium"
+source: |
+  type.inbound
+  and length(body.current_thread.text) > 120
+  and (
+    0 < length(body.links) < 8
+    and any([subject.subject, sender.display_name],
+            regex.icontains(., "(?:cloud|storage|mailbox)")
+    )
+  )
+  and (
+    any(file.explode(beta.message_screenshot()),
+        any(ml.nlu_classifier(.scan.ocr.raw).intents,
+            .name == "cred_theft" and .confidence == "high"
+        )
+        and regex.icontains(.scan.ocr.raw,
+                            "storage.{0,50}full",
+                            "free.{0,50}upgrade",
+                            "storage.{0,50}details",
+                            "storage.{0,50}quot",
+                            "(?:mailbox|cloud|account).{0,50}disabled",
+                            "(?:email|cloud|total).{0,50}storage"
+        )
+        and not strings.ilike(.scan.ocr.raw, "*free plan*")
+    )
+  )
+  and (
+    any(body.links,
+        // fingerprints of a hyperlinked image
+        .display_text is null
+        and .display_url.url is null
+        and (
+          .href_url.domain.root_domain in $free_file_hosts
+          or .href_url.domain.root_domain == "beehiiv.com"
+        )
+    )
+  )
+  
+  // and the sender is not from high trust sender root domains
+  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
+  )
+attack_types:
+  - "Credential Phishing"
+tactics_and_techniques:
+  - "Free file host"
+  - "Image as content"
+  - "Impersonation: Brand"
+  - "Social engineering"
+detection_methods:
+  - "Computer Vision"
+  - "Content analysis"
+  - "Header analysis"
+  - "Natural Language Understanding"
+  - "Optical Character Recognition"
+  - "Sender analysis"
+  - "URL analysis"
+id: "6c17535b-9ad1-5417-918e-f6dc344bdd92"
+og_id: "4c20f72c-0045-518c-8157-7dad5f196ecc"
+testing_pr: 3058
+testing_sha: 88b41e5d0b1ed305acb79d64ab160c195ec1653c