Suspicious recipients pattern with no Compauth pass and suspicious content

 1name: "Suspicious recipients pattern with no Compauth pass and suspicious content"
 2description: "Detects messages with undisclosed recipients (likely all bcc), where the Compauth verdict is not 'pass', and ML has identified suspicious language or credential phishing links."
 3type: "rule"
 4severity: "medium"
 5source: |
 6  type.inbound
 7  and (
 8    length(recipients.to) == 0
 9    or all(recipients.to, .display_name == "Undisclosed recipients")
10  )
11  and length(recipients.cc) == 0
12  and length(recipients.bcc) == 0
13  and 2 of (
14    (
15      any(headers.hops,
16          .authentication_results.compauth.verdict is not null
17          and .authentication_results.compauth.verdict not in ("pass", "softpass")
18      )
19    ),
20    (
21      any(ml.nlu_classifier(body.current_thread.text).intents,
22          .name in ("bec", "cred_theft", "advance_fee") and .confidence == "high"
23      )
24    ),
25    (
26      any(body.links,
27          any([ml.link_analysis(.)],
28              .credphish.disposition == "phishing"
29              and .credphish.confidence in ("high")
30          )
31      )
32    )
33  )
34  and (
35    profile.by_sender().prevalence in ("new", "outlier")
36    or (
37      profile.by_sender().any_messages_malicious_or_spam
38      and not profile.by_sender().any_messages_benign
39    )
40  )
41  // negate highly trusted sender domains unless they fail DMARC authentication
42  and (
43    (
44      sender.email.domain.root_domain in $high_trust_sender_root_domains
45      and not headers.auth_summary.dmarc.pass
46    )
47    or sender.email.domain.root_domain not in $high_trust_sender_root_domains
48  )  
49detection_methods:
50  - "Content analysis"
51  - "Computer Vision"
52  - "Header analysis"
53  - "Natural Language Understanding"
54  - "URL analysis"
55  - "URL screenshot"
56id: "34fb65f6-03e8-5752-b602-4f294172b5db"