PowerShell ScriptBlock: Send-MailMessage with -Attachments for Possible SMTP Data Exfiltration

title: "PowerShell ScriptBlock: Send-MailMessage with -Attachments for Possible SMTP Data Exfiltration"
id: 3eb25d1d-16fb-47e4-b3de-ed788c6fa416
status: test
description: This rule flags PowerShell script content that includes the Send-MailMessage cmdlet using the -Attachments parameter. Attackers can leverage email attachments to move data out of an environment over an external SMTP-based path. It relies on Script Block Logging telemetry that captures the executed script text.
references:
  - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1048.003/T1048.003.md#atomic-test-5---exfiltration-over-alternative-protocol---smtp
  - https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.utility/send-mailmessage?view=powershell-7.4
  - https://www.ietf.org/rfc/rfc2821.txt
  - https://github.com/SigmaHQ/sigma/blob/master/rules-threat-hunting/windows/powershell/powershell_script/posh_ps_send_mailmessage.yml
author: frack113, Huntrule Team
date: 2022-09-26
modified: 2024-11-01
tags:
  - attack.exfiltration
  - attack.t1048.003
  - detection.threat-hunting
logsource:
  product: windows
  category: ps_script
  definition: "Requirements: Script Block Logging must be enabled"
detection:
  selection:
    ScriptBlockText|contains: Send-MailMessage*-Attachments
  condition: selection
falsepositives:
  - Unknown
level: medium
license: DRL-1.1
related:
  - id: 9a7afa56-4762-43eb-807d-c3dc9ffe211b
    type: derived