[PR #3486] added rule: Brand impersonation: SharePoint PDF attachment with credential theft language

Author: github-actions[bot]

detection-rules/3486_brand_impersonation_sharepoint_pdf_cred_theft.yml

@@ -0,0 +1,114 @@
+name: "Brand impersonation: SharePoint PDF attachment with credential theft language"
+description: "PDF attachment contains SharePoint logo and high-confidence credential theft language detected via OCR analysis. The attachment includes URLs and originates from an unsolicited or low-reputation sender, excluding legitimate SharePoint file sharing notifications."
+type: "rule"
+severity: "medium"
+source: |
+  type.inbound
+  and (
+    any(attachments,
+        (
+          .file_type == "pdf"
+          and any(ml.logo_detect(.).brands, .name == "Microsoft SharePoint")
+          and any(file.explode(.), length(.scan.url.urls) > 0)
+          and any(file.explode(.),
+                  any(ml.nlu_classifier(.scan.ocr.raw).intents,
+                      .name == "cred_theft" and .confidence == "high"
+                  )
+          )
+        )
+    )
+  )
+  // negate sharepoint file share
+  and not (
+    // based on the message id format
+    (
+      (
+        strings.starts_with(headers.message_id, '<Share-')
+        and strings.ends_with(headers.message_id, '@odspnotify>')
+      )
+      or // negate legitimate access request to file
+   (
+        strings.starts_with(headers.message_id, '<Sharing')
+        and strings.ends_with(headers.message_id, '@odspnotify>')
+      )
+      // deal with Google thinking the message ID is "broke"
+      or (
+        strings.icontains(headers.message_id, 'SMTPIN_ADDED_BROKEN')
+        and any(headers.hops,
+                any(.fields,
+                    .name == "X-Google-Original-Message-ID"
+                    and strings.starts_with(.value, '<Share-')
+                    and strings.ends_with(.value, '@odspnotify>')
+                )
+        )
+      )
+    )
+    // all of the "action" links are sharepoint/ms
+    and all(filter(body.links,
+                   strings.icontains(subject.subject, .display_text)
+                   or .display_text == "Open"
+            ),
+            .href_url.domain.root_domain in ("sharepoint.com")
+            or (
+              .href_url.domain.tld == "ms"
+              // Microsoft does not own the .ms TLD, this checks to ensure it is one of their domains
+              and (
+                network.whois(.href_url.domain).registrant_company == "Microsoft Corporation"
+                or strings.ilike(network.whois(.href_url.domain).registrar_name,
+                                 "*MarkMonitor*",
+                                 "*CSC Corporate*",
+                                 "*com laude*"
+                )
+              )
+            )
+    )
+  )
+  and not (
+    (
+      (subject.is_reply or subject.is_forward)
+      and (
+        (length(headers.references) > 0 or headers.in_reply_to is not null)
+        // ensure that there are actual threads
+        and (
+          length(body.previous_threads) > 0
+          or (length(body.html.display_text) - length(body.current_thread.text)) > 200
+        )
+      )
+    )
+  )
+  and (
+    profile.by_sender_email().prevalence != 'common'
+    or not profile.by_sender_email().solicited
+    or profile.by_sender().any_messages_malicious_or_spam
+  )
+  and not profile.by_sender().any_messages_benign
+  
+  // 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
+  )
+
+attack_types:
+  - "Credential Phishing"
+tactics_and_techniques:
+  - "Impersonation: Brand"
+  - "Social engineering"
+  - "PDF"
+  - "Evasion"
+detection_methods:
+  - "Computer Vision"
+  - "File analysis"
+  - "Natural Language Understanding"
+  - "Optical Character Recognition"
+  - "Sender analysis"
+  - "URL analysis"
+  - "Header analysis"
+  - "Whois"
+id: "7c1528a6-d43a-5a0e-bb3f-8e642562a2f7"
+og_id: "ae3756fa-3751-5fba-b68d-d91164fd359c"
+testing_pr: 3486
+testing_sha: f33f1566624b885b185b895f19b606fabcfea537