sublimemediumRule

Attachment: PDF file with low reputation link to ZIP file (unsolicited)

Detects messages with PDF attachments linking directly to zip files from unsolicited senders.

MITRE ATT&CK

defense-evasion

Detection Query

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(.url, '\.(?:zip)')
                    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
  )
)

Author

Michael Tingle

Data Sources

Email MessagesEmail HeadersEmail Attachments

Platforms

Tags

Malfam: QakBot

Raw Content

name: "Attachment: PDF file with low reputation link to ZIP file (unsolicited)"
description: |
  Detects messages with PDF attachments linking directly to zip files from unsolicited senders.
type: "rule"
severity: "medium"
authors:
  - name: "Michael Tingle"
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(.url, '\.(?:zip)')
                      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: QakBot"
attack_types:
  - "Malware/Ransomware"
tactics_and_techniques:
  - "Evasion"
  - "PDF"
detection_methods:
  - "Archive analysis"
  - "File analysis"
  - "Natural Language Understanding"
  - "Sender analysis"
  - "URL analysis"
id: "d1ee2859-acd1-5c12-9b74-89439ed1eaf1"