Detection rules › Sublime MQL
Attachment: HTML smuggling with embedded base64-encoded ISO
HTML attachment contains a base-64 encoded ISO. This is a known TTP for multiple threat actors.
Threat classification
Sublime's own taxonomy (not MITRE ATT&CK).
| Category | Values |
|---|---|
| Attack types | Credential Phishing, Malware/Ransomware |
| Tactics and techniques | Evasion, HTML smuggling, ISO |
Event coverage
| Message attribute |
|---|
| attachments (collection) |
| type |
Rule body MQL
type.inbound
and any(attachments,
(
.file_extension in~ ("html", "htm")
or .file_extension in~ $file_extensions_common_archives
or .file_type == "html"
)
and any(file.explode(.),
any(.scan.strings.strings,
strings.ilike(.,
// Base64 encoded ISOs
"*SVNPIDk2NjAvSEZT*",
"*MTk5MyBFLllPVU5HREFMRQ*",
// Reversed base64 encoded ISOs
"*TZESvAjN2kDIPNVS*",
"*QRMFERH5UVPllLFByM5kTM*"
)
)
)
)
Detection logic
Scope: inbound message.
HTML attachment contains a base-64 encoded ISO. This is a known TTP for multiple threat actors.
- inbound message
any of
attachmentswhere all hold:any of:
- .file_extension in ('html', 'htm')
- .file_extension in $file_extensions_common_archives
- .file_type is 'html'
any of
file.explode(.)where:any of
.scan.strings.stringswhere:. matches any of 4 patterns
*SVNPIDk2NjAvSEZT**MTk5MyBFLllPVU5HREFMRQ**TZESvAjN2kDIPNVS**QRMFERH5UVPllLFByM5kTM*
Inspects: attachments[].file_extension, attachments[].file_type, type.inbound. Sensors: file.explode, strings.ilike. Reference lists: $file_extensions_common_archives.
Indicators matched (7)
| Field | Match | Value |
|---|---|---|
attachments[].file_extension | member | html |
attachments[].file_extension | member | htm |
attachments[].file_type | equals | html |
strings.ilike | substring | *SVNPIDk2NjAvSEZT* |
strings.ilike | substring | *MTk5MyBFLllPVU5HREFMRQ* |
strings.ilike | substring | *TZESvAjN2kDIPNVS* |
strings.ilike | substring | *QRMFERH5UVPllLFByM5kTM* |