Link: Direct link to riddle.com hosted showcase

 1name: "Link: Direct link to riddle.com hosted showcase"
 2description: "Message contains a single link to a Riddle.com hosted showcase which has been observed abused for credential phishing landing"
 3type: "rule"
 4severity: "medium"
 5source: |
 6  type.inbound
 7  and length(body.links) < 20
 8  and any(body.links,
 9          .href_url.domain.root_domain == "riddle.com"
10  )
11  and length(filter(body.links,
12                    .href_url.domain.root_domain == "riddle.com"
13                    and strings.istarts_with(.href_url.path, '/view/')
14             )
15  ) == 1
16  // negate highly trusted sender domains unless they fail DMARC authentication
17  and (
18    (
19      sender.email.domain.root_domain in $high_trust_sender_root_domains
20      and not headers.auth_summary.dmarc.pass
21    )
22    or sender.email.domain.root_domain not in $high_trust_sender_root_domains
23  )
24  and not profile.by_sender_email().any_messages_benign  
25tags:
26 - "Attack surface reduction"
27attack_types:
28  - "Credential Phishing"
29tactics_and_techniques:
30  - "Free file host"
31detection_methods:
32  - "Sender analysis"
33  - "URL analysis"
34  - "Header analysis"
35id: "cca7d2f5-421f-5421-ae13-da5588c15c8b"