Suspicious DocuSign Share From New Domain

 1name: "Suspicious DocuSign Share From New Domain"
 2description: "DocuSign shares with new reply-to addresses have been seen in recent attacks."
 3type: "rule"
 4severity: "high"
 5source: |
 6  type.inbound
 7
 8  // message is from docusign actual
 9  and sender.email.domain.root_domain == 'docusign.net'
10  and (headers.auth_summary.spf.pass or headers.auth_summary.dmarc.pass)
11
12  // 
13  // This rule makes use of a beta feature and is subject to change without notice
14  // using the beta feature in custom rules is not suggested until it has been formally released
15  // 
16
17  // reply-to email address has never been sent an email by the org
18  and not beta.profile.by_reply_to().solicited
19
20  // new reply-to
21  and any(headers.reply_to, network.whois(.email.domain).days_old < 30)
22
23  // not a completed DocuSign
24  and not strings.istarts_with(subject.subject, "Completed:")  
25tags:
26 - "Attack surface reduction"
27attack_types:
28  - "BEC/Fraud"
29  - "Credential Phishing"
30tactics_and_techniques:
31  - "Evasion"
32  - "Free file host"
33  - "Impersonation: Brand"
34  - "Social engineering"
35detection_methods:
36  - "Content analysis"
37  - "Header analysis"
38  - "Sender analysis"
39id: "d430a1f3-9a47-59b2-97fc-64b4792d5143"