Sublime Security high experimental mql

Attachment: Calendar file with invisible Unicode characters

Detects calendar (.ics) attachments containing suspicious invisible Unicode characters, which may be used to hide malicious content or bypass security filters. The rule triggers on messages with calendar-related keywords in the subject or body.

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Detection Logic

type.inbound
and not subject.is_reply
and any(attachments, .file_extension in~ ('ics'))
and any(attachments,
        any(file.explode(.),
            .file_extension in~ ('ics')
            and regex.icontains(.scan.strings.raw,
                                '[\x{E0000}-\x{E007F}\x{E0100}-\x{E01EF}\x{2062}\x{2064}]{8,}'
            )
        )
)
and (
  regex.icontains(subject.subject, '(calendar
| meeting
| event
| appointment)')
  or regex.icontains(body.current_thread.text,
                     '(calendar
| meeting
| event
| appointment)'
  )
  or any(attachments, .content_type in~ ("text/calendar"))
)

Field Validations

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