Detectionhightest

Suspicious AgentExecutor PowerShell Execution

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

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Launch

Nasreddine Bencherchali (Nextron Systems), memory-shardsCreated Sat Dec 24Updated Wed Aug 07c0b40568-b1e9-4b03-8d6c-b096da6da9abwindows

Log Source

WindowsProcess Creation

ProductWindows← raw: windows

CategoryProcess Creation← raw: process_creation

Events generated when a new process is spawned on the system. Covers command-line arguments, parent/child relationships, and process metadata.

Detection Logic

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_*