sublimehighRule

Service abuse: DocSend share from an unsolicited reply-to address

DocSend shares which contain a reply-to address or domain that has not been previously observed by the recipient organization.

MITRE ATT&CK

T1566 T1566.001 T1566.002 T1598 T1036 T1027

defense-evasioninitial-access

Detection Query

type.inbound

// Legitimate DocSend sending infratructure
and sender.email.email == "no-reply@docsend.com"

// 
// 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: DocSend share from an unsolicited reply-to address"
description: "DocSend shares which contain a reply-to address or domain that has not been previously observed by the recipient organization."
type: "rule"
severity: "high"
source: |
  type.inbound

  // Legitimate DocSend sending infratructure
  and sender.email.email == "no-reply@docsend.com"
  
  // 
  // 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:
  - "Credential Phishing"
tactics_and_techniques:
  - "Evasion"
  - "Free file host"
  - "Social engineering"
detection_methods:
  - "Content analysis"
  - "Header analysis"
  - "Sender analysis"
id: "b377e64c-21bd-5040-86ec-534e545a42db"