Sysmon Event ID 255: Sysmon service error report
Sysmon Event ID 255 records an internal Sysmon error condition.
- Applicable version
- Sysmon with this event enabled
- Last reviewed
- 2026-07-13
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
ID / Description
The error identifier and description explain which Sysmon component failed. Microsoft Q&A examples include RuleEngine and ServiceThread descriptions for schema incompatibility.
UtcTime
Use the timestamp to measure telemetry gaps around the error.
Computer
Prioritize hosts where Sysmon errors affect critical telemetry coverage.
Common 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 Events
MITRE ATT&CK Mapping
- T1562.001Impair 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.
Sysmon
| where EventID == 255
| project TimeGenerated, Computer, EventID, RenderedDescriptionindex=sysmon EventCode=255 | table _time, host, MessageUtcTime: 2026-07-13 03:08:00.000
ID: RuleEngine
Description: Registry rule version 4.22 is incompatible with Sysmon rule version 4.30
Computer: HOST01