• Sublime Core Feed
Medium Severity

Suspicious recipients pattern with no Compauth pass and suspicious content

Description

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.

References

No references.

Sublime Security
Created Aug 17th, 2023 • Last updated Aug 5th, 2025
Source
type.inbound
and (length(recipients.to) == 0 or all(recipients.to, .display_name == "Undisclosed recipients"))
and length(recipients.cc) == 0
and length(recipients.bcc) == 0
and 2 of (
  (
    any(headers.hops,
        .authentication_results.compauth.verdict is not null
        and .authentication_results.compauth.verdict not in ("pass", "softpass")
    )
  ),
  (
    any(ml.nlu_classifier(body.current_thread.text).intents,
        .name in ("bec", "cred_theft", "advance_fee") and .confidence == "high"
    )
  ),
  (
    any(body.links,
        any([ml.link_analysis(.)],
            .credphish.disposition == "phishing" and .credphish.confidence in ("high")
        )
    )
  )
)
and (
  profile.by_sender().prevalence in ("new", "outlier")
  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
)
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