sublimemediumRule

Attachment: PDF Attachment with links to workers.dev

Detects inbound messages containing PDF attachments with fewer than 5 pages that, when analyzed, contain URLs pointing to workers.dev subdomains. This pattern indicates potential abuse of Cloudflare Workers infrastructure to host malicious content delivered via PDF documents.

MITRE ATT&CK

T1566 T1566.001 T1566.002 T1598 T1036 T1027

defense-evasion

Detection Query

type.inbound
and any(filter(attachments, .file_type == "pdf"),
        beta.parse_exif(.).page_count <= 2
        and any(file.explode(.),
                any(.scan.url.urls, .domain.root_domain == "workers.dev")
        )
)

Data Sources

Email MessagesEmail HeadersEmail Attachments

Platforms

Raw Content

name: "Attachment: PDF Attachment with links to workers.dev"
description: "Detects inbound messages containing PDF attachments with fewer than 5 pages that, when analyzed, contain URLs pointing to workers.dev subdomains. This pattern indicates potential abuse of Cloudflare Workers infrastructure to host malicious content delivered via PDF documents."
type: "rule"
severity: "medium"
source: |
  type.inbound
  and any(filter(attachments, .file_type == "pdf"),
          beta.parse_exif(.).page_count <= 2
          and any(file.explode(.),
                  any(.scan.url.urls, .domain.root_domain == "workers.dev")
          )
  )
attack_types:
  - "Credential Phishing"
tactics_and_techniques:
  - "PDF"
  - "Free subdomain host"
  - "Evasion"
detection_methods:
  - "File analysis"
  - "Exif analysis"
  - "URL analysis"
id: "e8be2515-8b3d-5222-80da-6ecfad58341a"