{
  "author": "ckeller@fusioncybersecurity.us",
  "cat": "New Code Atypical Path",
  "detect": {
    "event": {
      "FILE_PATH": "C:\\Windows\\Temp\\3A22930E-7933-4932-A06B-DA4B7DB2FB1F\\mpextms.exe",
      "HASH": "c7b8517e59acf4d0fd72070c63d80aabff3e0f198eb66bfb06b4220e19223f55",
      "PROCESS_ID": 17988
    },
    "routing": {
      "arch": 2,
      "did": "",
      "event_id": "d47eb907-5575-4ffa-919f-a60bd10b49e0",
      "event_time": 1774468115845,
      "event_type": "NEW_DOCUMENT",
      "ext_ip": "23.128.32.10",
      "hostname": "desktop-3nfb237",
      "iid": "b2cd59fc-d09d-49e0-a9f2-1fd79ee9c175",
      "int_ip": "192.168.50.40",
      "latency": 5864,
      "moduleid": 2,
      "oid": "d3541070-8b0e-4663-8a6a-aa0727aacd36",
      "parent": "9727bc761f07cc5e5c90b93a69c43c07",
      "plat": 268435456,
      "sid": "ed8f7c3f-3a1a-493e-8fa4-35eb8c30b136",
      "tags": [
        "fusion-soc-alert",
        "fusion-soc-case",
        "fusion-soc-pulled",
        "fusion-soc-triage",
        "fusionsoc-critical",
        "fusionsoc-high",
        "fusionsoc-investigated",
        "qucikbooks",
        "windows",
        "yara_detection_memory"
      ],
      "this": "3a183707a0f991ae580862a969c43c18"
    }
  },
  "detect_id": "4d17014e-012c-4a87-975b-a06769c43c19",
  "gen_time": 1774468121709,
  "link": "https://app.limacharlie.io/orgs/d3541070-8b0e-4663-8a6a-aa0727aacd36/sensors/ed8f7c3f-3a1a-493e-8fa4-35eb8c30b136/timeline?time=1774468115\u0026selected=3a183707a0f991ae580862a969c43c18",
  "namespace": "general",
  "routing": {
    "arch": 2,
    "did": "",
    "event_id": "d47eb907-5575-4ffa-919f-a60bd10b49e0",
    "event_time": 1774468115845,
    "event_type": "NEW_DOCUMENT",
    "ext_ip": "23.128.32.10",
    "hostname": "desktop-3nfb237",
    "iid": "b2cd59fc-d09d-49e0-a9f2-1fd79ee9c175",
    "int_ip": "192.168.50.40",
    "latency": 5864,
    "moduleid": 2,
    "oid": "d3541070-8b0e-4663-8a6a-aa0727aacd36",
    "parent": "9727bc761f07cc5e5c90b93a69c43c07",
    "plat": 268435456,
    "sid": "ed8f7c3f-3a1a-493e-8fa4-35eb8c30b136",
    "tags": [
      "fusion-soc-alert",
      "fusion-soc-case",
      "fusion-soc-pulled",
      "fusion-soc-triage",
      "fusionsoc-critical",
      "fusionsoc-high",
      "fusionsoc-investigated",
      "qucikbooks",
      "windows",
      "yara_detection_memory"
    ],
    "this": "3a183707a0f991ae580862a969c43c18"
  },
  "source": "d3541070-8b0e-4663-8a6a-aa0727aacd36.b2cd59fc-d09d-49e0-a9f2-1fd79ee9c175.ed8f7c3f-3a1a-493e-8fa4-35eb8c30b136.10000000.2",
  "source_rule": "general.NEW FILE WRITE BYTES SAMPLE GRAB",
  "ts": 1774468121000
}

{
  "virustotal": {
    "malicious": false,
    "provider": "virustotal",
    "reputation": 0,
    "stats": {
      "confirmed-timeout": 0,
      "failure": 0,
      "harmless": 0,
      "malicious": 0,
      "suspicious": 0,
      "timeout": 0,
      "type-unsupported": 4,
      "undetected": 72
    }
  }
}

{
  "confidence": 0.95,
  "false_positive_reason": "Legitimate system binary staged in a temporary directory during an update or maintenance cycle.",
  "investigation_questions": [
    "Was this process spawned by a known update service like services.exe or TiWorker.exe?",
    "Are there any other files in the same temporary directory that appear suspicious?"
  ],
  "ioc_analysis": "The filename \u0027mpextms.exe\u0027 and the provided SHA-256 hash are verified as a clean Microsoft-signed binary (Microsoft Defender Browser Extension Native Message Host). The location is atypical for permanent execution but normal for staging during updates.",
  "iocs_extracted": [
    "c7b8517e59acf4d0fd72070c63d80aabff3e0f198eb66bfb06b4220e19223f55",
    "C:\\Windows\\Temp\\3A22930E-7933-4932-A06B-DA4B7DB2FB1F\\mpextms.exe"
  ],
  "mitre_techniques": [
    "T1036"
  ],
  "recommended_actions": [
    "Close case as false positive (unanimous AI verdict)",
    "Close as False Positive",
    "Add the specific hash to a global whitelist if the rule continues to trigger on legitimate updates",
    "Monitor for any subsequent suspicious activity from this process, though none is currently indicated"
  ],
  "risk_score": 8,
  "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 detected file \u0027mpextms.exe\u0027 with hash \u0027c7b8517e59acf4d0fd72070c63d80aabff3e0f198eb66bfb06b4220e19223f55\u0027 is a legitimate Microsoft Defender Browser Extension component. The execution from a temporary directory in C:\\Windows\\Temp\\ is common during automated updates or system maintenance tasks.\n\n**IOC Analysis:** The filename \u0027mpextms.exe\u0027 and the provided SHA-256 hash are verified as a clean Microsoft-signed binary (Microsoft Defender Browser Extension Native Message Host). The location is atypical for permanent execution but normal for staging during updates.\n\n---\n\n### \ud83e\udd16 qwen3.5:4b Analysis (Secondary + RAG)\n**Verdict:** false_positive | **Confidence:** 0.95\nThe detection is a false positive caused by Microsoft Windows Update processes running in the Temp directory. The process tree shows legitimate system binaries like svchost.exe and wuauclt.exe associated with this activity.\n\n**IOC Analysis:** mpextms.exe is a known Microsoft Windows Update helper process that runs from C:\\Windows\\Temp\\ during updates. The presence of MpSigStub.exe (Microsoft Signature Stub) running under SYSTEM confirms this is part of the Windows Update infrastructure, not malware.\n\n---\n\n### \ud83e\udd16 deepseek-r1:8b Analysis (Secondary + RAG)\n**Verdict:** false_positive | **Confidence:** 0.95\nThe detection event is likely a false positive, as mpextms.exe is associated with legitimate system processes like MpSigStub.exe, and no malicious activity was detected in the investigation.\n\n**IOC Analysis:** mpextms.exe is located in C:\\Windows\\Temp, which is common for temporary files and can be legitimate. The hash is not provided for validation, but the process spawned MpSigStub.exe, a benign system process for signature checking. Historical feedback and investigation results confirm no malicious intent.",
  "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 +RAG: false_positive (low, 95% confidence)",
      "deepseek-r1:8b +RAG: false_positive (informational, 95% confidence)"
    ],
    "votes": [
      {
        "confidence": 0.95,
        "model": "gemini-cli",
        "verdict": "false_positive"
      },
      {
        "confidence": 0.95,
        "had_rag": true,
        "model": "qwen3.5:4b",
        "verdict": "false_positive"
      },
      {
        "confidence": 0.95,
        "had_rag": true,
        "model": "deepseek-r1:8b",
        "verdict": "false_positive"
      }
    ],
    "winning_count": 3,
    "winning_verdict": "false_positive"
  }
}