sublimehighRule

Attachment: HTML smuggling with raw array buffer

Recursively scans files and archives to detect HTML smuggling techniques.

MITRE ATT&CK

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

defense-evasion

Detection Query

type.inbound
and any(attachments,
        (
          .file_extension in~ ("html", "htm", "shtml", "dhtml")
          or .file_extension in~ $file_extensions_common_archives
          or .file_type == "html"
        )
        and any(file.explode(.),
                any(.scan.strings.strings,
                    // arrayBuffer, eg repetition:
                    // [0xa0,0x8e,0xd0,0x60,...]
                    regex.icontains(., '(\W?0x[a-zA-Z0-9]{2}\W?,\s*){100}')
                )
                and any(.scan.strings.strings, strings.contains(., ".map"))
        )
)

Data Sources

Email MessagesEmail HeadersEmail Attachments

Platforms

References

https://playground.sublimesecurity.com?id=1c9531ea-f25b-41dc-9aeb-848a211293fb

Raw Content

name: "Attachment: HTML smuggling with raw array buffer"
description: |
  Recursively scans files and archives to detect HTML smuggling techniques.
references:
  - "https://playground.sublimesecurity.com?id=1c9531ea-f25b-41dc-9aeb-848a211293fb"
type: "rule"
severity: "high"
source: |
  type.inbound
  and any(attachments,
          (
            .file_extension in~ ("html", "htm", "shtml", "dhtml")
            or .file_extension in~ $file_extensions_common_archives
            or .file_type == "html"
          )
          and any(file.explode(.),
                  any(.scan.strings.strings,
                      // arrayBuffer, eg repetition:
                      // [0xa0,0x8e,0xd0,0x60,...]
                      regex.icontains(., '(\W?0x[a-zA-Z0-9]{2}\W?,\s*){100}')
                  )
                  and any(.scan.strings.strings, strings.contains(., ".map"))
          )
  )
attack_types:
  - "Credential Phishing"
  - "Malware/Ransomware"
tactics_and_techniques:
  - "Evasion"
  - "Free subdomain host"
  - "HTML smuggling"
detection_methods:
  - "Archive analysis"
  - "Content analysis"
  - "File analysis"
  - "Javascript analysis"
id: "a0d5c3dc-0763-5579-919e-456e5a37bd6f"