Medium Severity

Link: Credential phishing link with undisclosed recipients

Description

This rule detects messages with "Undisclosed Recipients" that contain a link to a credential phishing page.

References

No references.

Sublime Security
Created Aug 17th, 2023 • Last updated Aug 24th, 2026
Source
type.inbound
and (
  // No Recipients
  length(recipients.to) == 0
  or all(recipients.to, .display_name == "Undisclosed recipients")
)
and length(recipients.cc) == 0
and length(recipients.bcc) == 0
and (
  any(body.links,
      ml.link_analysis(.).credphish.disposition == "phishing"
      and ml.link_analysis(.).credphish.confidence in ("medium", "high")
  )
  or any(body.current_thread.links,
         regex.icount(.href_url.path, '\.[a-z]{2,}/') >= 2
         and not strings.icontains(.href_url.path, .href_url.domain.root_domain)
  )
)
// negate highly trusted sender domains unless they fail DMARC authentication
and not (
  sender.email.domain.root_domain in $high_trust_sender_root_domains
  and coalesce(headers.auth_summary.dmarc.pass, false)
)
and not profile.by_sender().solicited
and not profile.by_sender().any_messages_benign
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