Potential Data Exfiltration Over SMTP Via Send-MailMessage Cmdlet

SIGMA detection rule by frack113 · NOASSERTION

Detects the execution of a PowerShell script with a call to the "Send-MailMessage" cmdlet along with the "-Attachments" flag. This could be a potential sign of data exfiltration via Email. Adversaries may steal data by exfiltrating it over an un-encrypted network protocol other than that of the existing command and control channel. The data may also be sent to an alternate network location from the main command and control server.

title: Potential Data Exfiltration Over SMTP Via Send-MailMessage Cmdlet
id: 9a7afa56-4762-43eb-807d-c3dc9ffe211b
status: test
description: |
    Detects the execution of a PowerShell script with a call to the "Send-MailMessage" cmdlet along with the "-Attachments" flag. This could be a potential sign of data exfiltration via Email.
    Adversaries may steal data by exfiltrating it over an un-encrypted network protocol other than that of the existing command and control channel. The data may also be sent to an alternate network location from the main command and control server.
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
author: frack113
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
regression_tests_path: regression_data/rules-threat-hunting/windows/powershell/powershell_script/posh_ps_send_mailmessage/info.yml

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

306ce4ce-83dc-4563-8146-114218f7cfe0

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Executable code, not a declarative rule

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