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Detection rules › Sublime MQL

Attachment: Malformed OLE file

Severity
high
Type
rule
Source
github.com/sublime-security/sublime-rules

Attached OLE file (typically a Microsoft Office document) is malformed, possibly to evade traditional scanners and filters.

Threat classification

Sublime's own taxonomy (not MITRE ATT&CK).

CategoryValues
Attack typesCredential Phishing, Malware/Ransomware
Tactics and techniquesEvasion

Event coverage

Message attribute
attachments (collection)
type

Rule body MQL

type.inbound
and any(attachments,
        .file_extension in $file_extensions_macros
        and any(file.explode(.),
                any(.scan.yara.matches, .name == "MALFORMED_OLE_HEADER")
        )
)

Detection logic

Scope: inbound message.

Attached OLE file (typically a Microsoft Office document) is malformed, possibly to evade traditional scanners and filters.

  1. inbound message
  2. any of attachments where all hold:
    • .file_extension in $file_extensions_macros
    • any of file.explode(.) where:
      • any of .scan.yara.matches where:
        • .name is 'MALFORMED_OLE_HEADER'

Inspects: attachments[].file_extension, type.inbound. Sensors: file.explode. Reference lists: $file_extensions_macros.

Indicators matched (1)

FieldMatchValue
file.explode(attachments[])[].scan.yara.matches[].nameequalsMALFORMED_OLE_HEADER