Atomic Runbook: Lookup File Hash Entity Activity in Chronicle

ID: RB-ATOM-HASH-003 Version: 1.0 Last_Updated: 2025-05-30 Purpose: To retrieve a summary of a file hash's activity from Chronicle SIEM using the lookup_entity tool. This provides a quick overview of internal sightings (e.g., process executions, file observations), related alerts, and first/last seen times. Parent_Runbook(s)/Protocol(s): rules-bank/indicator_handling_protocols.md#3-atomic-indicator-file-hash Trigger: When a file hash requires an initial check for internal activity within Chronicle, often after external reputation checks.

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Inputs Required

• file_hash: string - The file hash (MD5, SHA1, SHA256) to look up.
  • Source Example: Alert data, output from rb_hash_get_gti_report.md.
• hours_back (optional): integer - How many hours of historical data to consider. Defaults to 72 (3 days).

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Execution Steps

1. Tool Selection:
   • Primary_Tool_MCP_Server: secops-mcp
   • Primary_Tool_Name: lookup_entity
2. Parameter Mapping:
   • Map file_hash (Input) to MCP Tool parameter entity_value.
   • Map hours_back (Input or default) to MCP Tool parameter hours_back.
3. Execute Tool: Call lookup_entity.
   • AI Agent Note: Refer to rules-bank/mcp_tool_best_practices.md.
4. Data Transformation/Extraction:
   • Output is textual. AI may parse for specific details (e.g., number of hosts, related alerts).

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Outputs Expected

• chronicle_entity_summary: string - Textual summary from lookup_entity.
• related_alerts_count (optional, if parsable): integer.
• hosts_observed_count (optional, if parsable): integer - Number of unique hosts where hash was seen.
• output_status: string - ["Success", "NoInfoFound", "Failure"]
• output_message: string (if Failure).

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Decision Logic / Next Steps (If Applicable)

• IF output_status is "Success":
  • Log chronicle_entity_summary.
  • IF related_alerts_count > 0 OR hosts_observed_count > 0 (or summary indicates sightings) THEN
    • Flag Hash for "Further Internal Investigation - Activity Observed".
    • Proceed to rb_hash_search_process_events_chronicle.md for detailed execution logs.
  • ELSE
    • Flag Hash as "No Internal Activity Observed via Lookup".
• IF output_status is "NoInfoFound":
  • Log "No activity found for file hash {file_hash} in Chronicle for the last {hours_back} hours."
• ELSE (output_status is "Failure"):
  • Log error: output_message.
  • Escalate: "Failed to lookup file hash {file_hash} in Chronicle."

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AI Agent Execution Notes

• Default hours_back is 72. Adjust as needed.
• AI parsing chronicle_entity_summary should look for "Observed on hosts:", "Related Alerts:", "File Executions:".

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Metrics Collection Points

• Log execution time.
• Log output_status.
• (Reference rules-bank/ai_performance_logging_requirements.md)

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References

• rules-bank/mcp_tool_best_practices.md
• rules-bank/indicator_handling_protocols.md
• rules-bank/ai_performance_logging_requirements.md