Create link_single_riddle.yml (#3037)

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

Author: 3 people

detection-rules/link_single_riddle.yml

@@ -0,0 +1,35 @@
+name: "Link: Direct link to riddle.com hosted showcase"
+description: "Message contains a single link to a Riddle.com hosted showcase which has been observed abused for credential phishing landing"
+type: "rule"
+severity: "medium"
+source: |
+  type.inbound
+  and length(body.links) < 20
+  and any(body.links,
+          .href_url.domain.root_domain == "riddle.com"
+  )
+  and length(filter(body.links,
+                    .href_url.domain.root_domain == "riddle.com"
+                    and strings.istarts_with(.href_url.path, '/view/')
+             )
+  ) == 1
+  // 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_email().any_messages_benign
+tags:
+ - "Attack surface reduction"
+attack_types:
+  - "Credential Phishing"
+tactics_and_techniques:
+  - "Free file host"
+detection_methods:
+  - "Sender analysis"
+  - "URL analysis"
+  - "Header analysis"
+id: "cca7d2f5-421f-5421-ae13-da5588c15c8b"