Detection rules › Sublime MQL
Service abuse: DocuSign share from an unsolicited reply-to address
DocuSign shares which contain a reply-to address or domain that has not been previously observed by the recipient organization.
Threat classification
Sublime's own taxonomy (not MITRE ATT&CK).
| Category | Values |
|---|---|
| Attack types | Credential Phishing |
| Tactics and techniques | Evasion, Free file host, Social engineering |
Event coverage
Rule body MQL
type.inbound
// message is from docusign actual
and sender.email.domain.root_domain == 'docusign.net'
and not any(headers.reply_to, .email.domain.domain == 'docusign.com')
and (headers.auth_summary.spf.pass or headers.auth_summary.dmarc.pass)
// not a completed DocuSign
// reminders are sent automatically and can be just as malicious as the initial
// users often decline malicious ones
and not strings.istarts_with(subject.subject, "Completed: ")
and not strings.istarts_with(subject.subject, "Here is your signed document: ")
and not strings.istarts_with(subject.subject, "Voided: ")
//
// 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 rarely seen in org
and beta.profile.by_reply_to().prevalence in~ ("new", "rare")
// 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.
DocuSign shares which contain a reply-to address or domain that has not been previously observed by the recipient organization.
- inbound message
- sender.email.domain.root_domain is 'docusign.net'
not:
any of
headers.reply_towhere:- .email.domain.domain is 'docusign.com'
any of:
- headers.auth_summary.spf.pass
- headers.auth_summary.dmarc.pass
not:
- subject.subject starts with 'Completed: '
not:
- subject.subject starts with 'Here is your signed document: '
not:
- subject.subject starts with 'Voided: '
- beta.profile.by_reply_to().prevalence in ('new', 'rare')
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.pass, headers.reply_to, headers.reply_to[].email.domain.domain, sender.email.domain.root_domain, subject.subject, type.inbound. Sensors: beta.profile.by_reply_to, strings.istarts_with.
Indicators matched (5)
| Field | Match | Value |
|---|---|---|
sender.email.domain.root_domain | equals | docusign.net |
headers.reply_to[].email.domain.domain | equals | docusign.com |
strings.istarts_with | prefix | Completed: |
strings.istarts_with | prefix | Here is your signed document: |
strings.istarts_with | prefix | Voided: |