Detection rules › Sublime MQL
Service abuse: Dropbox share from an unsolicited reply-to address
This rule detects Dropbox share notifications which contain a reply-to address or domain that has not been previously observed sending messages to or receiving messages from the recipient organization.
Threat classification
Sublime's own taxonomy (not MITRE ATT&CK).
| Category | Values |
|---|---|
| Attack types | Callback Phishing, BEC/Fraud |
| Tactics and techniques | Evasion, Social engineering |
Event coverage
| Message attribute |
|---|
| headers.auth_summary |
| sender.email |
| subject |
| type |
Rule body MQL
type.inbound
// Legitimate Dropbox sending infratructure
and sender.email.email == "no-reply@dropbox.com"
and headers.auth_summary.spf.pass
and headers.auth_summary.dmarc.pass
and strings.ends_with(headers.auth_summary.spf.details.designator,
'.dropbox.com'
)
and strings.icontains(subject.subject, 'shared')
and strings.icontains(subject.subject, 'with you')
//
// This rule makes use of a beta feature and is subject to change without notice
// using the beta feature in custom rules is not suggested until it has been formally released
//
// reply-to address has never sent an email to the org
and beta.profile.by_reply_to().prevalence == "new"
// reply-to email address has never been sent an email by the org
and not beta.profile.by_reply_to().solicited
// do not match if the reply_to address has been observed as a reply_to address
// of a message that has been classified as benign
and not beta.profile.by_reply_to().any_messages_benign
Detection logic
Scope: inbound message.
This rule detects Dropbox share notifications which contain a reply-to address or domain that has not been previously observed sending messages to or receiving messages from the recipient organization.
- inbound message
- sender.email.email is 'no-reply@dropbox.com'
- headers.auth_summary.spf.pass
- headers.auth_summary.dmarc.pass
- headers.auth_summary.spf.details.designator ends with '.dropbox.com'
- subject.subject contains 'shared'
- subject.subject contains 'with you'
- beta.profile.by_reply_to().prevalence is 'new'
not:
- beta.profile.by_reply_to().solicited
not:
- beta.profile.by_reply_to().any_messages_benign
Inspects: headers.auth_summary.dmarc.pass, headers.auth_summary.spf.details.designator, headers.auth_summary.spf.pass, sender.email.email, subject.subject, type.inbound. Sensors: beta.profile.by_reply_to, strings.ends_with, strings.icontains.
Indicators matched (4)
| Field | Match | Value |
|---|---|---|
sender.email.email | equals | no-reply@dropbox.com |
strings.ends_with | suffix | .dropbox.com |
strings.icontains | substring | shared |
strings.icontains | substring | with you |