image-load-sched-task-ms-office (#566)

rules/windows/persistence_suspicious_image_load_scheduled_task_ms_office.toml

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+[metadata]
+creation_date = "2020/11/17"
+ecs_version = ["1.6.0"]
+maturity = "production"
+updated_date = "2020/11/17"
+
+[rule]
+author = ["Elastic"]
+description = """
+Identifies a suspicious image load (taskschd.dll) from Microsoft Office processes. This behavior may indicate
+adversarial activity where a scheduled task is configured via Windows Component Object Model (COM). This technique can
+be used to configure persistence and evade monitoring by avoiding the usage of the traditional Windows binary
+(schtasks.exe) used to manage scheduled tasks.
+"""
+index = ["winlogbeat-*", "logs-endpoint.events.*"]
+language = "eql"
+license = "Elastic License"
+name = "Suspicious Image Load (taskschd.dll) from MS Office"
+references = [
+    "https://medium.com/threatpunter/detecting-adversary-tradecraft-with-image-load-event-logging-and-eql-8de93338c16",
+    "https://www.clearskysec.com/wp-content/uploads/2020/10/Operation-Quicksand.pdf",
+]
+risk_score = 21
+rule_id = "baa5d22c-5e1c-4f33-bfc9-efa73bb53022"
+severity = "low"
+tags = ["Elastic", "Host", "Windows", "Threat Detection", "Execution"]
+type = "eql"
+
+query = '''
+library where process.name in ("WINWORD.EXE", "EXCEL.EXE", "POWERPNT.EXE", "MSPUB.EXE", "MSACCESS.EXE") and
+  event.action == "load" and
+  event.category == "library" and
+  file.name == "taskschd.dll"
+'''
+
+
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+[[rule.threat.technique]]
+id = "T1053"
+name = "Scheduled Task/Job"
+reference = "https://attack.mitre.org/techniques/T1053/"
+
+
+[rule.threat.tactic]
+id = "TA0003"
+name = "Persistence"
+reference = "https://attack.mitre.org/tactics/TA0003/"
+