sublimehighRule

Attachment: Self-sender PDF with minimal content and view prompt

Detects messages where the sender and recipient are the same address with a PDF attachment containing only 'VIEW PDF' text and a standardized body message requesting to view the attachment.

MITRE ATT&CK

T1566 T1566.001 T1566.002 T1598 T1204.002 T1486 T1036 T1027

initial-accessdefense-evasion

Detection Query

type.inbound
// self sender
and length(recipients.to) == 1
and (
  sender.email.email == recipients.to[0].email.email
  or recipients.to[0].email.domain.valid == false
)
and strings.starts_with(body.current_thread.text, 'Please see attached')
and any(filter(attachments, .file_type == 'pdf'),
        any(file.explode(.),
            .scan.strings.strings[0] == 'VIEW PDF'
            and length(.scan.strings.strings) == 1
        )
)

Data Sources

Email MessagesEmail HeadersEmail Attachments

Platforms

Raw Content

name: "Attachment: Self-sender PDF with minimal content and view prompt"
description: "Detects messages where the sender and recipient are the same address with a PDF attachment containing only 'VIEW PDF' text and a standardized body message requesting to view the attachment."
type: "rule"
severity: "high"
source: |
  type.inbound
  // self sender
  and length(recipients.to) == 1
  and (
    sender.email.email == recipients.to[0].email.email
    or recipients.to[0].email.domain.valid == false
  )
  and strings.starts_with(body.current_thread.text, 'Please see attached')
  and any(filter(attachments, .file_type == 'pdf'),
          any(file.explode(.),
              .scan.strings.strings[0] == 'VIEW PDF'
              and length(.scan.strings.strings) == 1
          )
  )
attack_types:
  - "Credential Phishing"
  - "Malware/Ransomware"
tactics_and_techniques:
  - "PDF"
  - "Social engineering"
  - "Evasion"
detection_methods:
  - "Content analysis"
  - "File analysis"
  - "Sender analysis"
id: "07670a8c-4e64-5807-8c9e-97171c076884"