{
  "author": "_ext-sigma-7a14fbc3-54d9-4b4d-8700-61eddada04f0[bulk][segment]",
  "cat": "Change PowerShell Policies to an Insecure Level",
  "detect": {
    "event": {
      "BASE_ADDRESS": 9764864,
      "COMMAND_LINE": "\"C:\\Windows\\SysWOW64\\WindowsPowerShell\\v1.0\\powershell.exe\" -NoLogo -NonInteractive -NoProfile -ExecutionPolicy Bypass -Force Stop-Process -Name remote_webauthn",
      "FILE_IS_SIGNED": 1,
      "FILE_PATH": "C:\\Windows\\SysWOW64\\WindowsPowerShell\\v1.0\\powershell.exe",
      "HASH": "3bfedaaa40d9e19e45a3ee10c0f14b1750b01619ebb9f39be3865bcfdacdd2e5",
      "MEMORY_USAGE": 57729024,
      "PARENT": {
        "BASE_ADDRESS": 14942208,
        "COMMAND_LINE": "C:\\Windows\\syswow64\\MsiExec.exe -Embedding 57917046E265CB85396AB79820287388 E Global\\MSI0000",
        "FILE_IS_SIGNED": 1,
        "FILE_PATH": "C:\\Windows\\syswow64\\MsiExec.exe",
        "HASH": "34e2e75cb8622809e4f95b3e665071d755870f503167268f23d0110cc5f7ee2c",
        "MEMORY_USAGE": 13615104,
        "PARENT_ATOM": "23a7a08840c587c857088e4669c19e54",
        "PARENT_PROCESS_ID": 26224,
        "PROCESS_ID": 32732,
        "THIS_ATOM": "0077d031151f6ea2ed35db9269c19e54",
        "THREADS": 7,
        "TIMESTAMP": 1774296660033,
        "USER_NAME": "NT AUTHORITY\\SYSTEM"
      },
      "PARENT_PROCESS_ID": 32732,
      "PROCESS_ID": 35844,
      "THREADS": 27,
      "USER_NAME": "NT AUTHORITY\\SYSTEM"
    },
    "routing": {
      "arch": 2,
      "did": "",
      "event_id": "8983927d-378e-4fd5-bd1d-518a8a248529",
      "event_time": 1774296665572,
      "event_type": "NEW_PROCESS",
      "ext_ip": "23.128.32.10",
      "hostname": "desktop-atsepsk",
      "iid": "b2cd59fc-d09d-49e0-a9f2-1fd79ee9c175",
      "int_ip": "192.168.50.200",
      "latency": -162,
      "moduleid": 2,
      "oid": "d3541070-8b0e-4663-8a6a-aa0727aacd36",
      "parent": "0077d031151f6ea2ed35db9269c19e54",
      "plat": 268435456,
      "sid": "8f3a47be-5629-4c66-921d-17c39ed07e87",
      "tags": [
        "fusion-soc-alert",
        "fusion-soc-case",
        "fusion-soc-pulled",
        "fusion-soc-triage",
        "fusionsoc-critical",
        "fusionsoc-high",
        "fusionsoc-investigated",
        "joys",
        "windows",
        "yara_detection_memory",
        "yara_detection_disk"
      ],
      "this": "4a44c56e7ae628a0e4c8da2569c19e5a"
    }
  },
  "detect_id": "7023e176-d25b-45a0-8fec-a9e369c19e59",
  "detect_mtd": {
    "author": "frack113",
    "description": "Detects changing the PowerShell script execution policy to a potentially insecure level using the \"-ExecutionPolicy\" flag.",
    "falsepositives": [
      "Administrator scripts"
    ],
    "level": "medium",
    "references": [
      "https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.security/set-executionpolicy?view=powershell-7.4",
      "https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_execution_policies?view=powershell-7.4",
      "https://adsecurity.org/?p=2604",
      "https://thedfirreport.com/2021/11/01/from-zero-to-domain-admin/"
    ],
    "tags": [
      "attack.execution",
      "attack.t1059.001"
    ]
  },
  "gen_time": 1774296665411,
  "link": "https://app.limacharlie.io/orgs/d3541070-8b0e-4663-8a6a-aa0727aacd36/sensors/8f3a47be-5629-4c66-921d-17c39ed07e87/timeline?time=1774296665\u0026selected=4a44c56e7ae628a0e4c8da2569c19e5a",
  "namespace": "general",
  "routing": {
    "arch": 2,
    "did": "",
    "event_id": "8983927d-378e-4fd5-bd1d-518a8a248529",
    "event_time": 1774296665572,
    "event_type": "NEW_PROCESS",
    "ext_ip": "23.128.32.10",
    "hostname": "desktop-atsepsk",
    "iid": "b2cd59fc-d09d-49e0-a9f2-1fd79ee9c175",
    "int_ip": "192.168.50.200",
    "latency": -162,
    "moduleid": 2,
    "oid": "d3541070-8b0e-4663-8a6a-aa0727aacd36",
    "parent": "0077d031151f6ea2ed35db9269c19e54",
    "plat": 268435456,
    "sid": "8f3a47be-5629-4c66-921d-17c39ed07e87",
    "tags": [
      "fusion-soc-alert",
      "fusion-soc-case",
      "fusion-soc-pulled",
      "fusion-soc-triage",
      "fusionsoc-critical",
      "fusionsoc-high",
      "fusionsoc-investigated",
      "joys",
      "windows",
      "yara_detection_memory",
      "yara_detection_disk"
    ],
    "this": "4a44c56e7ae628a0e4c8da2569c19e5a"
  },
  "rule_tags": [
    "attack.execution",
    "attack.t1059.001",
    "ext:ext-sigma"
  ],
  "source": "d3541070-8b0e-4663-8a6a-aa0727aacd36.b2cd59fc-d09d-49e0-a9f2-1fd79ee9c175.8f3a47be-5629-4c66-921d-17c39ed07e87.10000000.2",
  "source_rule": "service.windows_process_creation/proc_creation_win_powershell_set_policies_to_unsecure_level",
  "ts": 1774296665000
}

{
  "virustotal": {
    "malicious": false,
    "provider": "virustotal",
    "reputation": 0,
    "stats": {
      "confirmed-timeout": 0,
      "failure": 0,
      "harmless": 0,
      "malicious": 0,
      "suspicious": 0,
      "timeout": 11,
      "type-unsupported": 4,
      "undetected": 61
    }
  }
}

{
  "confidence": 0.917,
  "false_positive_reason": "legitimate_software_update",
  "investigation_questions": [
    "Was a Chrome Remote Desktop update or install scheduled on this host?"
  ],
  "ioc_analysis": "The process \u0027powershell.exe\u0027 and its parent \u0027MsiExec.exe\u0027 are both legitimate Microsoft-signed binaries running from expected system directories. The command line \u0027-ExecutionPolicy Bypass\u0027 is a standard installer technique to ensure script execution, and \u0027remote_webauthn\u0027 is a known-good component of Google Chrome Remote Desktop.",
  "iocs_extracted": [
    "C:\\Windows\\SysWOW64\\WindowsPowerShell\\v1.0\\powershell.exe",
    "C:\\Windows\\syswow64\\MsiExec.exe",
    "remote_webauthn"
  ],
  "mitre_techniques": [
    "T1059.001",
    "T1562.001"
  ],
  "recommended_actions": [
    "Close case as false positive (unanimous AI verdict)",
    "Whitelists known-good installers using PowerShell with execution policy bypass in this context.",
    "No further investigation required."
  ],
  "risk_score": 10,
  "severity": "low",
  "summary": "**Vote: UNANIMOUS (3/3 -\u003e FALSE POSITIVE)**\n\n### \u264a gemini-cli Analysis (Primary)\n**Verdict:** false_positive | **Confidence:** 0.95\nThe detection triggered on a PowerShell execution policy bypass used by the Windows Installer (MsiExec.exe) to stop the \u0027remote_webauthn\u0027 process, which is a legitimate component of Chrome Remote Desktop. This is a common pattern during software updates or uninstalls where an installer script gracefully terminates associated processes before modification.\n\n**IOC Analysis:** The process \u0027powershell.exe\u0027 and its parent \u0027MsiExec.exe\u0027 are both legitimate Microsoft-signed binaries running from expected system directories. The command line \u0027-ExecutionPolicy Bypass\u0027 is a standard installer technique to ensure script execution, and \u0027remote_webauthn\u0027 is a known-good component of Google Chrome Remote Desktop.\n\n---\n\n### \ud83e\udd16 qwen3.5:4b Analysis (Secondary)\n**Verdict:** false_positive | **Confidence:** 0.9\nThis detection is a false positive because the process tree shows legitimate Microsoft-signed binaries executing scheduled maintenance tasks under SYSTEM context. The PowerShell execution policy bypass is part of a standard Windows Update or SCCM management operation.\n\n**IOC Analysis:** The process path C:\\Windows\\SysWOW64\\WindowsPowerShell\\v1.0\\powershell.exe is the expected location for legitimate PowerShell. The parent process MsiExec.exe running under SYSTEM context indicates this is likely a scheduled task executing MSI-based maintenance or policy updates. The execution policy bypass is commonly used by legitimate management tools during automated deployments.\n\n---\n\n### \ud83e\udd16 deepseek-r1:8b Analysis (Secondary)\n**Verdict:** false_positive | **Confidence:** 0.9\nThe detection event involves a PowerShell process created by a legitimate MsiExec.exe process, running from a standard system location and signed. The command-line does not indicate malicious activity, and historical feedback confirms false positives for this rule.\n\n**IOC Analysis:** The FILE_PATH is in the expected location for PowerShell.exe and is signed. The parent process, MsiExec.exe, is a legitimate system binary. The command-line arguments do not show policy changes or malicious intent, and the high-privilege user context (SYSTEM) can be legitimate for system tasks.",
  "verdict": "false_positive",
  "voting": {
    "auto_action": "auto_close_fp",
    "mode": "unanimous",
    "total_models": 3,
    "vote_summary": [
      "gemini-cli: false_positive (low, 95% confidence)",
      "qwen3.5:4b: false_positive (low, 90% confidence)",
      "deepseek-r1:8b: false_positive (low, 90% confidence)"
    ],
    "votes": [
      {
        "confidence": 0.95,
        "model": "gemini-cli",
        "verdict": "false_positive"
      },
      {
        "confidence": 0.9,
        "model": "qwen3.5:4b",
        "verdict": "false_positive"
      },
      {
        "confidence": 0.9,
        "model": "deepseek-r1:8b",
        "verdict": "false_positive"
      }
    ],
    "winning_count": 3,
    "winning_verdict": "false_positive"
  }
}