New Rule: Link to auto-downloaded DMG in archive (#1063)

Co-authored-by: ID Generator <[email protected]>

detection-rules/link_download_dmg_in_archive.yml

@@ -0,0 +1,48 @@
+name: "Link to auto-downloaded DMG in archive"
+description: "A link in the body of the message downloads an archive containing a DMG file. The message is not from a common or trusted sender and is unsolicited."
+type: "rule"
+severity: "medium"
+source: |
+  type.inbound
+  and any(body.links,
+          any(beta.linkanalysis(.).files_downloaded,
+              .file_extension in~ $file_extensions_common_archives
+              and any(file.explode(.), .file_extension == "dmg")
+          )
+  )
+  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_false_positives
+    )
+  )
+  
+  // negate highly trusted sender domains unless they fail DMARC authentication
+  and (
+    (
+      sender.email.domain.root_domain in $high_trust_sender_root_domains
+      and (
+        any(distinct(headers.hops, .authentication_results.dmarc is not null),
+            strings.ilike(.authentication_results.dmarc, "*fail")
+        )
+      )
+    )
+    or sender.email.domain.root_domain not in $high_trust_sender_root_domains
+  )
+
+tags:
+  - "Attack surface reduction"
+attack_types:
+  - "Malware/Ransomware"
+tactics_and_techniques:
+  - "Evasion"
+detection_methods:
+  - "Archive analysis"
+  - "File analysis"
+  - "Sender analysis"
+  - "URL analysis"
+id: "dc04cdd8-6023-578b-a0d5-c59f4b76cacd"