sublimemediumRule

Service abuse: Free provider with SendGrid routing

Message From header includes a free email provider domain but is routed through SendGrid infrastructure, indicating potential service abuse for delivery evasion.

MITRE ATT&CK

T1566 T1566.001 T1566.002 T1598 T1036 T1027

defense-evasion

Detection Query

type.inbound
and sender.email.domain.domain in $free_email_providers
and any(headers.domains, .root_domain == "sendgrid.net")
and not any(ml.nlu_classifier(body.current_thread.text).intents,
            .name == "benign"
)
and not any(ml.nlu_classifier(body.current_thread.text).topics,
            .name == "Bounce Back and Delivery Failure Notifications"
)

Data Sources

Email MessagesEmail HeadersEmail Attachments

Platforms

Tags

Attack surface reduction

Raw Content

name: "Service abuse: Free provider with SendGrid routing"
description: "Message From header includes a free email provider domain but is routed through SendGrid infrastructure, indicating potential service abuse for delivery evasion."
type: "rule"
severity: "medium"
source: |
  type.inbound
  and sender.email.domain.domain in $free_email_providers
  and any(headers.domains, .root_domain == "sendgrid.net")
  and not any(ml.nlu_classifier(body.current_thread.text).intents,
              .name == "benign"
  )
  and not any(ml.nlu_classifier(body.current_thread.text).topics,
              .name == "Bounce Back and Delivery Failure Notifications"
  )
  
tags:
  - "Attack surface reduction"
attack_types:
  - "Credential Phishing"
tactics_and_techniques:
  - "Free email provider"
  - "Evasion"
detection_methods:
  - "Header analysis"
  - "Sender analysis"
id: "3079cacb-2ab9-533a-bced-59545bd54d63"