Detection rules › Sublime MQL

Attachment with high risk VBA macro (unsolicited)

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

Potentially malicious attachment containing a VBA macro. Oletools categorizes the macro risk as 'high'.

Threat classification

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

CategoryValues
Attack typesMalware/Ransomware
Tactics and techniquesMacros

Event coverage

Rule body MQL

type.inbound
and any(attachments,
        (
          .file_extension in~ $file_extensions_macros
          or (
            .file_extension is null
            and .file_type == "unknown"
            and .content_type == "application/octet-stream"
            and .size < 100000000
          )
        )
        and file.oletools(.).indicators.vba_macros.risk == "high"
)
and (
  not profile.by_sender().solicited
  or (
    profile.by_sender().any_messages_malicious_or_spam
    and not profile.by_sender().any_messages_benign
  )
)

Detection logic

Scope: inbound message.

Potentially malicious attachment containing a VBA macro. Oletools categorizes the macro risk as 'high'.

  1. inbound message
  2. any of attachments where all hold:
    • any of:
      • .file_extension in $file_extensions_macros
      • all of:
        • .file_extension is missing
        • .file_type is 'unknown'
        • .content_type is 'application/octet-stream'
        • .size < 100000000
    • file.oletools(.).indicators.vba_macros.risk is 'high'
  3. any of:
    • not:
      • profile.by_sender().solicited
    • all of:
      • profile.by_sender().any_messages_malicious_or_spam
      • not:
        • profile.by_sender().any_messages_benign

Inspects: attachments[].content_type, attachments[].file_extension, attachments[].file_type, attachments[].size, type.inbound. Sensors: file.oletools, profile.by_sender. Reference lists: $file_extensions_macros.

Indicators matched (2)

FieldMatchValue
attachments[].file_typeequalsunknown
attachments[].content_typeequalsapplication/octet-stream