GCP Audit Logs - Detect Bulk VM Snapshot Deletion

// Update these thresholds if noisy in your environment
let SnapshotDeletionThreshold = 10;
let TimeWindow = 1m;
GCPAuditLogs
| where ServiceName == "compute.googleapis.com"
| where MethodName has "compute.snapshots.delete"
| where GCPResourceType == "gce_snapshot" and Severity == "NOTICE"
| extend 
    AuthzInfoJson = parse_json(AuthorizationInfo),
    RequestMetadataJson = parse_json(RequestMetadata),
    ResponseJson = parse_json(Response)
| extend PermissionType = tostring(AuthzInfoJson[0].permissionType)
| where PermissionType == "ADMIN_WRITE"
| extend 
    CallerIpAddress = tostring(RequestMetadataJson.callerIp),
    UserAgent = tostring(RequestMetadataJson.callerSuppliedUserAgent),
    SnapshotName = extract(@"snapshots/([^/]+)", 1, GCPResourceName),
    OperationType = tostring(ResponseJson.operationType),
    OperationId = tostring(ResponseJson.id)
| summarize 
    SnapshotCount = count(),
    SnapshotList = make_set(SnapshotName, 100),
    FirstDeletion = min(TimeGenerated),
    LastDeletion = max(TimeGenerated),
    OperationIds = make_set(OperationId, 100),
    CallerIPs = make_set(CallerIpAddress, 10)
    by PrincipalEmail, ProjectId, UserAgent
| where SnapshotCount >= SnapshotDeletionThreshold
| extend DeletionTimeSpan = LastDeletion - FirstDeletion
| where DeletionTimeSpan <= TimeWindow
| extend 
    AccountName = tostring(split(PrincipalEmail, "@")[0]), 
    AccountUPNSuffix = tostring(split(PrincipalEmail, "@")[1])
| project 
    TimeGenerated = FirstDeletion,
    PrincipalEmail,
    ProjectId,
    SnapshotCount,
    SnapshotList,
    FirstDeletion,
    LastDeletion,
    DeletionTimeSpan,
    CallerIPs,
    UserAgent,
    OperationIds,
    AccountName,
    AccountUPNSuffix

name: GCP Audit Logs - Detect Bulk VM Snapshot Deletion
kind: Scheduled
tags:
- GCP
- Compute
- Data Destruction
- Cloud Security
tactics:
- Impact
- DefenseEvasion
triggerThreshold: 0
triggerOperator: gt
version: 1.0.0
status: Available
alertDetailsOverride:
  alertDisplayNameFormat: 'Bulk VM Snapshot Deletion: {{SnapshotCount}} snapshots deleted by {{PrincipalEmail}} in {{ProjectId}}'
  alertDescriptionFormat: |-
    User {{PrincipalEmail}} deleted {{SnapshotCount}} VM snapshots in project {{ProjectId}} within a short time period. 
    This may indicate ransomware, data destruction, or defense evasion activity. Verify authorization, check remaining snapshots, review IP addresses, and investigate for compromise.    
queryFrequency: 15m
id: dfdffdc7-929f-4c7e-8f48-30e5ffddb067
requiredDataConnectors:
- connectorId: GCPAuditLogsDefinition
  dataTypes:
  - GCPAuditLogs
relevantTechniques:
- T1485
- T1490
- T1562.001
description: |
  'Detects bulk deletion of Google Cloud VM snapshots within a short time period, which may indicate data destruction or defense evasion activities.
  VM snapshots are critical for backup and disaster recovery. Bulk deletion of snapshots can prevent recovery from incidents and may indicate
  malicious activity such as ransomware, data destruction, or an attempt to cover tracks after a security breach.
  Adversaries may delete snapshots to maximize damage, prevent forensic investigation, or hinder recovery efforts.
  This rule triggers when multiple snapshots are deleted by the same user within a 1-minute window.'  
customDetails:
  LastDeletion: LastDeletion
  DeletionTimeSpan: DeletionTimeSpan
  FirstDeletion: FirstDeletion
  CallerIPs: CallerIPs
  SnapshotList: SnapshotList
  UserAgent: UserAgent
  ProjectId: ProjectId
  SnapshotCount: SnapshotCount
entityMappings:
- entityType: Account
  fieldMappings:
  - columnName: PrincipalEmail
    identifier: FullName
  - columnName: AccountName
    identifier: Name
  - columnName: AccountUPNSuffix
    identifier: UPNSuffix
- entityType: CloudApplication
  fieldMappings:
  - columnName: ProjectId
    identifier: Name
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Google Cloud Platform Audit Logs/Analytic Rules/GCPBulkVMSnapshotDeletion.yaml
queryPeriod: 15m
severity: High
query: |
  // Update these thresholds if noisy in your environment
  let SnapshotDeletionThreshold = 10;
  let TimeWindow = 1m;
  GCPAuditLogs
  | where ServiceName == "compute.googleapis.com"
  | where MethodName has "compute.snapshots.delete"
  | where GCPResourceType == "gce_snapshot" and Severity == "NOTICE"
  | extend 
      AuthzInfoJson = parse_json(AuthorizationInfo),
      RequestMetadataJson = parse_json(RequestMetadata),
      ResponseJson = parse_json(Response)
  | extend PermissionType = tostring(AuthzInfoJson[0].permissionType)
  | where PermissionType == "ADMIN_WRITE"
  | extend 
      CallerIpAddress = tostring(RequestMetadataJson.callerIp),
      UserAgent = tostring(RequestMetadataJson.callerSuppliedUserAgent),
      SnapshotName = extract(@"snapshots/([^/]+)", 1, GCPResourceName),
      OperationType = tostring(ResponseJson.operationType),
      OperationId = tostring(ResponseJson.id)
  | summarize 
      SnapshotCount = count(),
      SnapshotList = make_set(SnapshotName, 100),
      FirstDeletion = min(TimeGenerated),
      LastDeletion = max(TimeGenerated),
      OperationIds = make_set(OperationId, 100),
      CallerIPs = make_set(CallerIpAddress, 10)
      by PrincipalEmail, ProjectId, UserAgent
  | where SnapshotCount >= SnapshotDeletionThreshold
  | extend DeletionTimeSpan = LastDeletion - FirstDeletion
  | where DeletionTimeSpan <= TimeWindow
  | extend 
      AccountName = tostring(split(PrincipalEmail, "@")[0]), 
      AccountUPNSuffix = tostring(split(PrincipalEmail, "@")[1])
  | project 
      TimeGenerated = FirstDeletion,
      PrincipalEmail,
      ProjectId,
      SnapshotCount,
      SnapshotList,
      FirstDeletion,
      LastDeletion,
      DeletionTimeSpan,
      CallerIPs,
      UserAgent,
      OperationIds,
      AccountName,
      AccountUPNSuffix