Common Event Format (CEF) via AMA - Critical or High Severity Detections by User

id: 4465ebde-b381-45f7-ad08-7d818070a11c
name: Common Event Format (CEF) via AMA - Critical or High Severity Detections by User
description: |
  'Creates an incident when a large number of Critical or High severity CrowdStrike Falcon sensor detections is triggered by a single user within 1 hour. The rule uses the CrowdStrikeFalconEventStream table, filters for DetectionSummaryEvent records with Severity set to Critical or High, and alerts when detections for a single DstUserName exceed the configured threshold of 15. Review DstHostName, SrcIpAddr, FileName, FileHash, and Message for investigation context.'
severity: High
status: Available
requiredDataConnectors:
  - connectorId: CefAma
    dataTypes:
      - CommonSecurityLog
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics: 
- Impact
- DefenseEvasion
relevantTechniques:
- T1489
- T1562
query: |
  let timeframe = 1h;
  let threshold = 15; // update threshold value based on organization's preference
  let NotableEvents = CrowdStrikeFalconEventStream
  | where TimeGenerated > ago(timeframe)
  | where EventType == "DetectionSummaryEvent"
  | where Severity in ("Critical", "High")
  | summarize StartTimeUtc = min(TimeGenerated), EndTimeUtc = max(TimeGenerated), Total = count() by DstUserName, DstHostName, SrcIpAddr, FileName, FileHash, Message
  | where Total > threshold;
  NotableEvents
  | extend timestamp = StartTimeUtc, AccountCustomEntity = DstUserName, HostCustomEntity = DstHostName, IPCustomEntity = SrcIpAddr, FileHashCustomEntity = FileHash, FileHashAlgo = "MD5"
  | project timestamp, StartTimeUtc, EndTimeUtc, DstUserName, DstHostName, SrcIpAddr, FileName, FileHash, FileHashAlgo, Message, Total, AccountCustomEntity, HostCustomEntity, IPCustomEntity, FileHashCustomEntity
entityMappings:
- entityType: Account
  fieldMappings:
  - identifier: FullName
    columnName: AccountCustomEntity
- entityType: Host
  fieldMappings:
  - identifier: FullName
    columnName: HostCustomEntity
- entityType: IP
  fieldMappings:
  - identifier: Address
    columnName: IPCustomEntity
- entityType: FileHash
  fieldMappings:
  - identifier: Algorithm
    columnName: FileHashAlgo
  - identifier: Value
    columnName: FileHashCustomEntity
alertDetailsOverride:
  alertDisplayNameFormat: 'CrowdStrike critical/high detections by user: {{DstUserName}}'
  alertDescriptionFormat: User {{DstUserName}} generated {{Total}} critical/high detections from host {{DstHostName}}.
customDetails:
  DstUserName: DstUserName
  DstHostName: DstHostName
  SrcIpAddr: SrcIpAddr
  FileName: FileName
  FileHash: FileHash
  Total: Total
version: 1.0.6
kind: Scheduled