{
  "id": "255",
  "source": "sysmon",
  "priority": "P3",
  "applicable_version": "Sysmon with this event enabled",
  "last_reviewed": "2026-07-13",
  "source_url": "https://learn.microsoft.com/en-us/sysinternals/downloads/sysmon",
  "category": "Service",
  "name": "Sysmon service error report",
  "definition": "Sysmon Event ID 255 records an internal Sysmon error condition.",
  "trigger_scenarios": "Microsoft documents that this event is generated when an error occurs within Sysmon, including heavy load, tasks that could not be performed, a Sysmon service bug, or security and integrity conditions not being met.",
  "key_fields": [
    {
      "field": "ID / Description",
      "explanation": "The error identifier and description explain which Sysmon component failed. Microsoft Q&A examples include RuleEngine and ServiceThread descriptions for schema incompatibility."
    },
    {
      "field": "UtcTime",
      "explanation": "Use the timestamp to measure telemetry gaps around the error."
    },
    {
      "field": "Computer",
      "explanation": "Prioritize hosts where Sysmon errors affect critical telemetry coverage."
    }
  ],
  "false_positives": [
    "High system load and Sysmon bugs can generate this event without attacker activity.",
    "Configuration schema mismatches after upgrades can produce RuleEngine or ServiceThread errors until the configuration is rebuilt."
  ],
  "related_event_ids": [
    "4",
    "16"
  ],
  "attck_mapping": [
    {
      "technique_id": "T1562.001",
      "technique_name": "Impair Defenses: Disable or Modify Tools"
    }
  ],
  "detection_notes": "Use threshold=1 on high-value hosts when Event 255 contains ID=DriverCommunication, RuleEngine, ServiceThread, or another error that creates a telemetry gap. Microsoft documents Event 255 for Sysmon internal errors and notes security/integrity conditions may be involved; treat it as T1562.001 only when it follows service stop, configuration change, driver unload, or unexplained loss of Events 1/3/11. Correlate with Events 4 and 16 and verify whether the Sysmon schema/configuration version changed before escalating.",
  "kql_snippet": "Sysmon\n| where EventID == 255\n| project TimeGenerated, Computer, EventID, RenderedDescription",
  "spl_snippet": "index=sysmon EventCode=255 | table _time, host, Message",
  "sample_log": "UtcTime: 2026-07-13 03:08:00.000\nID: RuleEngine\nDescription: Registry rule version 4.22 is incompatible with Sysmon rule version 4.30\nComputer: HOST01",
  "route": "/sysmon-events/255/",
  "canonical_url": "https://soceventlookup.com/sysmon-events/255/",
  "json_url": "/api/events/sysmon/255.json"
}