Detection rules › Sublime MQL
Attachment: Archive with embedded CHM file
Recursively scans files and archives to detect embedded CHM (Microsoft Compiled HTML Help) files. According to CERT-UA, on March 7, 2022, phishing attacks targeted state organizations of Ukraine using Zip files with embedded CHM documents, which themselves contained malicious VBScript inside a .htm file. The activity is associated with UNC1151, according to CERT-UA.
Threat classification
Sublime's own taxonomy (not MITRE ATT&CK).
| Category | Values |
|---|---|
| Attack types | Malware/Ransomware |
| Tactics and techniques | Evasion |
Event coverage
| Message attribute |
|---|
| attachments (collection) |
| type |
Rule body MQL
type.inbound
and any(attachments,
.file_extension in~ $file_extensions_common_archives
and any(file.explode(.), .file_extension =~ "chm")
)
Detection logic
Scope: inbound message.
Recursively scans files and archives to detect embedded CHM (Microsoft Compiled HTML Help) files. According to CERT-UA, on March 7, 2022, phishing attacks targeted state organizations of Ukraine using Zip files with embedded CHM documents, which themselves contained malicious VBScript inside a .htm file. The activity is associated with UNC1151, according to CERT-UA.
- inbound message
any of
attachmentswhere all hold:- .file_extension in $file_extensions_common_archives
any of
file.explode(.)where:- .file_extension is 'chm'
Inspects: attachments[].file_extension, type.inbound. Sensors: file.explode. Reference lists: $file_extensions_common_archives.
Indicators matched (1)
| Field | Match | Value |
|---|---|---|
file.explode(attachments[])[].file_extension | equals | chm |