sublimehighRule

Attachment: HTML file with excessive padding and suspicious patterns

Attached HTML file contains excessive line breaks and suspicious Javascript patterns.

MITRE ATT&CK

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

defense-evasion

Detection Query

type.inbound
and any(attachments,
        (
          .content_type == "text/html"
          or .file_extension in~ ("html", "htm", "shtml", "dhtml")
          or .file_type == "html"
        )
        and any(file.explode(.),
                any(.scan.yara.matches, .name == "HTML_EXCESSIVE_PADDING")
        )
)

Data Sources

Email MessagesEmail HeadersEmail Attachments

Platforms

Raw Content

name: "Attachment: HTML file with excessive padding and suspicious patterns"
description: |
  Attached HTML file contains excessive line breaks and suspicious Javascript patterns.
type: "rule"
severity: "high"
source: |
  type.inbound
  and any(attachments,
          (
            .content_type == "text/html"
            or .file_extension in~ ("html", "htm", "shtml", "dhtml")
            or .file_type == "html"
          )
          and any(file.explode(.),
                  any(.scan.yara.matches, .name == "HTML_EXCESSIVE_PADDING")
          )
  )
attack_types:
  - "Credential Phishing"
  - "Malware/Ransomware"
tactics_and_techniques:
  - "Evasion"
  - "HTML smuggling"
detection_methods:
  - "File analysis"
  - "HTML analysis"
  - "YARA"
id: "0a6aee1e-df58-5f1e-8f49-477ed61babe5"