Self-impersonation: Sender matches recipient with bolded name and suspicious link

name: "Self-impersonation: Sender matches recipient with bolded name and suspicious link"
description: "Detects messages where the sender's email address matches the recipient's email address, with the sender's display name appearing in bold text and a suspicious 'Read the Message' link present in the body."
type: "rule"
severity: "medium"
source: |
  type.inbound
  // sender matches recipients
  and (
    length(recipients.to) == 1
    and recipients.to[0].email.email == sender.email.email
  )
  // sender in current thread BOLD
  and any(html.xpath(body.html, '//b').nodes,
          .display_text == sender.display_name
  )
  // we want the dashed html element to contain a link, and that link to include part of the subject (the subject is the org)
  and any(html.xpath(body.html,
                     '//table//td[contains(@style, "border-style: dashed") and contains(@style, "border-width: 1pt")]//a[./b]'
          ).nodes,
          any(regex.extract(subject.base, '(?P<word>\w+)'),
              any(..links,
                  strings.icontains(.href_url.url, ..named_groups["word"])
              )
          )
  )
attack_types:
  - "Credential Phishing"
tactics_and_techniques:
  - "Evasion"
  - "Social engineering"
detection_methods:
  - "Header analysis"
  - "HTML analysis"
  - "Sender analysis"
id: "0129a805-2fe2-5a40-81bc-b3459085aa23"