Suspicious AgentExecutor PowerShell Execution

SIGMA detection rule by Nasreddine Bencherchali (Nextron Systems), memory-shards · NOASSERTION

Detects execution of the AgentExecutor.exe binary. Which can be abused as a LOLBIN to execute powershell scripts with the ExecutionPolicy "Bypass" or any binary named "powershell.exe" located in the path provided by 6th positional argument

title: Suspicious AgentExecutor PowerShell Execution
id: c0b40568-b1e9-4b03-8d6c-b096da6da9ab
related:
    - id: 7efd2c8d-8b18-45b7-947d-adfe9ed04f61
      type: similar
status: test
description: Detects execution of the AgentExecutor.exe binary. Which can be abused as a LOLBIN to execute powershell scripts with the ExecutionPolicy "Bypass" or any binary named "powershell.exe" located in the path provided by 6th positional argument
author: Nasreddine Bencherchali (Nextron Systems), memory-shards
references:
    - https://twitter.com/lefterispan/status/1286259016436514816
    - https://lolbas-project.github.io/lolbas/OtherMSBinaries/Agentexecutor/
    - https://learn.microsoft.com/en-us/mem/intune/apps/intune-management-extension
    - https://twitter.com/jseerden/status/1247985304667066373/photo/1
date: 2022-12-24
modified: 2024-08-07
tags:
    - attack.stealth
    - attack.t1218
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith: '\AgentExecutor.exe'
        - OriginalFileName: 'AgentExecutor.exe'
    selection_cli:
        # Example:
        #   AgentExecutor.exe -powershell [scriptPath] [outputFilePath] [errorFilePath] [timeoutFilePath] [timeoutSeconds] [powershellPath] [enforceSignatureCheck] [runAs32BitOn64]
        # Note:
        #   - If [timeoutSeconds] is NULL then it defaults to 60000
        #   - If [enforceSignatureCheck] is:
        #       - "NULL" or "1" then a PowerShell instance is spawned with the args: "-NoProfile -executionPolicy allsigned -file "
        #       - Else a PowerShell instance is spawned with the args: "-NoProfile -executionPolicy bypass -file "
        #   - [powershellPath] is always concatendated to "powershell.exe"
        CommandLine|contains:
            - ' -powershell' # Also covers the "-powershellDetection" flag
            - ' -remediationScript'
    filter_main_pwsh:
        CommandLine|contains:
            - 'C:\Windows\System32\WindowsPowerShell\v1.0\'
            - 'C:\Windows\SysWOW64\WindowsPowerShell\v1.0\'
    filter_main_intune:
        ParentImage|endswith: '\Microsoft.Management.Services.IntuneWindowsAgent.exe'
    condition: all of selection_* and not 1 of filter_main_*
falsepositives:
    - Unknown
level: high

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

037b851f-e5bc-45ae-a0f3-953b7e4dedc5

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Executable code, not a declarative rule

This submission is arbitrary [[ currentRule.format ? currentRule.format.toUpperCase() : '' ]] code, not a declarative detection rule — review it as you would any script before running it, and note that it cannot be safely aggregated or auto-executed alongside YARA/Sigma/Suricata/CRS rules.

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