sublimemediumRule

Service abuse: Adobe Sign notification from an unsolicited reply-to address

Identifies messages appearing to come from Adobe Sign signature notifications that contain a reply-to address not previously seen in organizational communications. This tactic exploits trust in legitimate Adobe services while attempting to establish unauthorized communication channels.

MITRE ATT&CK

T1566.002 T1534 T1656 T1566.003 T1598 T1566 T1598.003

initial-access

Detection Query

type.inbound

// Legitimate Adobe Sign sending infratructure
and sender.email.email == "adobesign@adobesign.com"
and headers.auth_summary.spf.pass
and headers.auth_summary.dmarc.pass
and strings.icontains(subject.subject, 'signature requested')

//
// 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

Data Sources

Email MessagesEmail HeadersEmail Attachments

Platforms

Tags

Attack surface reduction

Raw Content

name: "Service abuse: Adobe Sign notification from an unsolicited reply-to address"
description: "Identifies messages appearing to come from Adobe Sign signature notifications that contain a reply-to address not previously seen in organizational communications. This tactic exploits trust in legitimate Adobe services while attempting to establish unauthorized communication channels."
type: "rule"
severity: "medium"
source: |
  type.inbound
  
  // Legitimate Adobe Sign sending infratructure
  and sender.email.email == "adobesign@adobesign.com"
  and headers.auth_summary.spf.pass
  and headers.auth_summary.dmarc.pass
  and strings.icontains(subject.subject, 'signature requested')
  
  //
  // 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

tags:
 - "Attack surface reduction"
attack_types:
  - "BEC/Fraud"
  - "Callback Phishing"
  - "Spam"
tactics_and_techniques:
  - "Social engineering"
  - "Impersonation: Brand"
detection_methods:
  - "Header analysis"
  - "Sender analysis"
id: "d00893ba-a65a-5b04-88d1-f35512eae291"