Attachment: PDF file with low reputation links to suspicious filetypes (unsolicited)

name: "Attachment: PDF file with low reputation links to suspicious filetypes (unsolicited)"
description: |
  Detects messages with PDF attachments linking directly to suspicious filetypes on hosts with low reputation from unsolicited senders.
type: "rule"
severity: "medium"
source: |
  type.inbound
  and any(ml.nlu_classifier(body.current_thread.text).entities,
          .name == "request"
  )
  and any(attachments,
          .file_extension == "pdf"
          and any(file.explode(.),
                  any(.scan.pdf.urls,
                      regex.contains(.path,
                                     '\.(?:exe|cab|vbs|ps1|rar|iso|dll|one|lnk|sh)\b'
                      )
                      and .domain.root_domain not in $tranco_1m
                  )
          )
  )
  and (
    not profile.by_sender().solicited
    or (
      profile.by_sender().any_messages_malicious_or_spam
      and not profile.by_sender().any_messages_benign
    )
  )
tags:
  - "Malfam: Ave Maria"
attack_types:
  - "Malware/Ransomware"
tactics_and_techniques:
  - "Evasion"
  - "PDF"
detection_methods:
  - "Archive analysis"
  - "File analysis"
  - "Sender analysis"
id: "6144f880-a4f0-5776-b7cc-2f89d3bb5000"