Brand impersonation: DocSend

name: "Brand impersonation: DocSend"
description: |
  Attack impersonating DocSend.
references:
  - "https://docsend.com"
type: "rule"
severity: "high"
source: |
  type.inbound
  and (
    (
      sender.display_name =~ 'DocSend'
      or strings.ilevenshtein(sender.display_name, 'DocSend') <= 1
      or strings.icontains(sender.email.domain.domain, '*docsend*')
      or regex.icontains(body.current_thread.text, 'on Dropbox\s*(?:Doc)?\s*Send')
      or regex.icontains(body.current_thread.text,
                         'The Dropbox\s*(?:Doc)?\s*Send Team'
      )
      or regex.icontains(body.current_thread.text,
                         'Report to Dropbox\s*(?:Doc)?\s*Send'
      )
      or regex.icontains(body.current_thread.text,
                         '©\s*20[0-9]{2}\s*,\s*Dropbox DocSend'
      )
      or any(ml.nlu_classifier(body.current_thread.text).entities,
             .name in ("sender", "org")
             and strings.icontains(.text, 'Dropbox DocSend')
      )
    )
  )
  and not (
    sender.email.domain.root_domain in~ ('docsend.com')
    and coalesce(headers.auth_summary.dmarc.pass, false)
  )
  and not profile.by_sender_email().solicited
  
  // 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
  )

attack_types:
  - "Credential Phishing"
tactics_and_techniques:
  - "Impersonation: Brand"
  - "Lookalike domain"
  - "Social engineering"
detection_methods:
  - "Header analysis"
  - "Sender analysis"
id: "cd9a3f7a-bda2-5cf9-9a0f-8acef23711a3"