Suspicious Execution of Powershell with Base64 (via process_creation)

title: Suspicious Execution of Powershell with Base64 (via process_creation)
id: 4c07a074-f93e-567a-b377-377f80d2552e
status: stable
description: This rule detects commandline to launch powershell with a base64 payload
references:
    - https://attack.mitre.org/techniques/T1059/001/
    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1059.001/T1059.001.md#atomic-test-20---powershell-invoke-known-malicious-cmdlets
    - https://unit42.paloaltonetworks.com/unit42-pulling-back-the-curtains-on-encodedcommand-powershell-attacks/
    - https://mikefrobbins.com/2017/06/15/simple-obfuscation-with-powershell-using-base64-encoding/
author: Huntrule Team
date: 2026-04-11
tags:
    - attack.execution
    - attack.t1059.001
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - \powershell.exe
            - \pwsh.exe
        CommandLine|contains:
            - ' -e '
            - ' -en '
            - ' -enc '
            - ' -enco'
            - ' -ec '
    filter_encoding:
        CommandLine|contains: ' -Encoding '
    filter_azure:
        ParentImage|contains:
            - 'C:\Packages\Plugins\Microsoft.GuestConfiguration.ConfigurationforWindows\'
            - '\gc_worker.exe'
    condition: selection and not 1 of filter_*
falsepositives:
    - Unknown
level: medium