Detection rules › Sublime MQL
Link: Microsoft protected message with matching sender and recipient addresses
Detects when a user receives a protected message (RPMSG) with the to and from headers matching.
Threat classification
Sublime's own taxonomy (not MITRE ATT&CK).
| Category | Values |
|---|---|
| Attack types | Credential Phishing |
| Tactics and techniques | Evasion, Social engineering |
Event coverage
Rule body MQL
type.inbound
// contains the rpmsg
and any(attachments,
.file_extension == "rpmsg"
or .content_type == "application/x-microsoft-rpmsg-message"
)
// contains the proper link
and any(body.links,
.href_url.domain.root_domain == "office365.com"
and (
strings.icontains(.href_url.query_params, "InternetMessageID=")
or strings.icontains(.href_url.path, '/Encryption/retrieve.ashx')
)
)
// the To and From headers are the same
and length(recipients.to) == 1
and all(recipients.to, .email.email == sender.email.email)
Detection logic
Scope: inbound message.
Detects when a user receives a protected message (RPMSG) with the to and from headers matching.
- inbound message
any of
attachmentswhere any holds:- .file_extension is 'rpmsg'
- .content_type is 'application/x-microsoft-rpmsg-message'
any of
body.linkswhere all hold:- .href_url.domain.root_domain is 'office365.com'
any of:
- .href_url.query_params contains 'InternetMessageID='
- .href_url.path contains '/Encryption/retrieve.ashx'
- length(recipients.to) is 1
all of
recipients.towhere:- .email.email is sender.email.email
Inspects: attachments[].content_type, attachments[].file_extension, body.links, body.links[].href_url.domain.root_domain, body.links[].href_url.path, body.links[].href_url.query_params, recipients.to, recipients.to[].email.email, sender.email.email, type.inbound. Sensors: strings.icontains.
Indicators matched (5)
| Field | Match | Value |
|---|---|---|
attachments[].file_extension | equals | rpmsg |
attachments[].content_type | equals | application/x-microsoft-rpmsg-message |
body.links[].href_url.domain.root_domain | equals | office365.com |
strings.icontains | substring | InternetMessageID= |
strings.icontains | substring | /Encryption/retrieve.ashx |