Attachment: Fake Slack installer

name: "Attachment: Fake Slack installer"
description: |
  HTML attachment contains a Slack logo, request language, and a link to an executable. Observed in the wild.
type: "rule"
severity: "high"
source: |
  type.inbound
  and (
    any(attachments,
        (
          .file_extension in~ ("html", "htm", "shtml", "dhtml")
          or .file_type == "html"
          or .content_type == "text/html"
        )
        and any(ml.logo_detect(file.html_screenshot(.)).brands,
                .name == "Slack" and .confidence in ("medium", "high")
        )
        and any(ml.nlu_classifier(file.parse_html(.).display_text).entities,
                .name == "request" and .text =~ "download"
        )
        and any(file.explode(.),
                any(.scan.url.urls,
                    strings.iends_with(.path, ".exe")
                    and .domain.root_domain not in $org_domains
                )
        )
    )
  )
attack_types:
  - "Malware/Ransomware"
tactics_and_techniques:
  - "Evasion"
  - "HTML smuggling"
  - "Impersonation: Brand"
  - "Scripting"
  - "Social engineering"
detection_methods:
  - "Archive analysis"
  - "Computer Vision"
  - "File analysis"
  - "HTML analysis"
  - "Natural Language Understanding"
  - "URL analysis"
id: "cded2d2f-a5ca-5754-9f2a-d6bdf28baab4"