sublimehighRule

Attachment: OLE external relationship containing file scheme link to executable filetype

This rule identifies attachments containing file scheme links pointing to executable file types, a common indicator of malware distribution. It applies to various suspicious file extensions and archive formats, aiming to prevent the initiation and execution of malicious software.

MITRE ATT&CK

T1566.001 T1204.002 T1486 T1036 T1027

defense-evasion

Detection Query

type.inbound
and any(attachments,
        (
          .file_extension in~ $file_extensions_macros
          or .file_extension in~ $file_extensions_common_archives
          or (
            .file_extension is null
            and .file_type == "unknown"
            and .content_type == "application/octet-stream"
            and .size < 100000000
          )
        )
        and length(file.oletools(.).relationships) < 500
        and any(file.oletools(.).relationships,
                .target_url.scheme == "file"
                and regex.icontains(.target_url.path,
                                    '\.(action|ahk|apk|app|appimage|applescript|bat|bin|cab|cmd|command|cpl|dll|dmg|exe|gadget|hta|inf|ins|ipa|isu|jar|job|js|jse|lnk|msi|msp|paf|pif|ps1|rgs|run|scr|sct|sh|shb|vb|vbe|vbs)($|[^\w])'
                )
                // avoid flagging on internal/network drives mappings
                and not (
                  strings.starts_with(.target_url.scheme, "file")
                  and not regex.imatch(.target_url.path, '/?[a-z]:/')
                )
        )
)
and (
  not profile.by_sender().any_messages_benign
  or profile.by_sender().any_messages_malicious_or_spam
)

Data Sources

Email MessagesEmail HeadersEmail Attachments

Platforms

Tags

Attack surface reductionMalfam: PikabotMalfam: DarkGate

Raw Content

name: "Attachment: OLE external relationship containing file scheme link to executable filetype"
description: "This rule identifies attachments containing file scheme links pointing to executable file types, a common indicator of malware distribution. It applies to various suspicious file extensions and archive formats, aiming to prevent the initiation and execution of malicious software."
type: "rule"
severity: "high"
source: |
  type.inbound
  and any(attachments,
          (
            .file_extension in~ $file_extensions_macros
            or .file_extension in~ $file_extensions_common_archives
            or (
              .file_extension is null
              and .file_type == "unknown"
              and .content_type == "application/octet-stream"
              and .size < 100000000
            )
          )
          and length(file.oletools(.).relationships) < 500
          and any(file.oletools(.).relationships,
                  .target_url.scheme == "file"
                  and regex.icontains(.target_url.path,
                                      '\.(action|ahk|apk|app|appimage|applescript|bat|bin|cab|cmd|command|cpl|dll|dmg|exe|gadget|hta|inf|ins|ipa|isu|jar|job|js|jse|lnk|msi|msp|paf|pif|ps1|rgs|run|scr|sct|sh|shb|vb|vbe|vbs)($|[^\w])'
                  )
                  // avoid flagging on internal/network drives mappings
                  and not (
                    strings.starts_with(.target_url.scheme, "file")
                    and not regex.imatch(.target_url.path, '/?[a-z]:/')
                  )
          )
  )
  and (
    not profile.by_sender().any_messages_benign
    or profile.by_sender().any_messages_malicious_or_spam
  )

tags:
  - "Attack surface reduction"
  - "Malfam: Pikabot"
  - "Malfam: DarkGate"
attack_types:
  - "Malware/Ransomware"
tactics_and_techniques:
  - "Evasion"
detection_methods:
  - "Archive analysis"
  - "Content analysis"
  - "OLE analysis"
  - "Sender analysis"

id: "33bf6fd4-b170-5da2-808a-ffe74af6e21b"