Sigma rule: Potential Data Exfiltration Over SMTP Via Send-MailMessage Cmdlet

Rule

Title

Potential Data Exfiltration Over SMTP Via Send-MailMessage Cmdlet

Status

test

Level

medium

Author

frack113

Date

2022-09-26

Modified

2024-11-01

File

rules-threat-hunting/windows/powershell/powershell_script/posh_ps_send_mailmessage.yml

Commit

ccbb0369507f796db0b0ae6854c8a2be471b9d84

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.

Log source

product

windows

category

ps_script

definition

Requirements: Script Block Logging must be enabled

Detection

selection:
    ScriptBlockText|contains: 'Send-MailMessage*-Attachments'
condition: selection

False positives (as the rule lists them)

• Unknown

Tags

• attack.exfiltration
• attack.t1048.003
• detection.threat-hunting

MITRE ATT&CK ids this rule names

• T1048.003

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

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules-threat-hunting/windows/powershell/powershell_script/posh_ps_send_mailmessage.yml