Link: Credential phishing link with undisclosed recipients

name: "Link: Credential phishing link with undisclosed recipients"
description: |
  This rule detects messages with "Undisclosed Recipients" that contain a link to a credential phishing page. 
type: "rule"
severity: "medium"
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")
  )
  // 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().solicited
  and not profile.by_sender().any_messages_benign

attack_types:
  - "Credential Phishing"
tactics_and_techniques:
  - "Evasion"
detection_methods:
  - "Computer Vision"
  - "Header analysis"
  - "URL screenshot"
id: "06fc155e-f779-50a7-ad5f-3c3777fbf8f5"