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

tags:
- GCP
- Compute
- Data Destruction
- Cloud Security
queryFrequency: 15m
kind: Scheduled
version: 1.0.0
relevantTechniques:
- T1485
- T1490
- T1562.001
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.    
triggerOperator: gt
customDetails:
  CallerIPs: CallerIPs
  UserAgent: UserAgent
  SnapshotList: SnapshotList
  DeletionTimeSpan: DeletionTimeSpan
  ProjectId: ProjectId
  LastDeletion: LastDeletion
  FirstDeletion: FirstDeletion
  SnapshotCount: SnapshotCount
status: Available
requiredDataConnectors:
- connectorId: GCPAuditLogsDefinition
  dataTypes:
  - GCPAuditLogs
id: dfdffdc7-929f-4c7e-8f48-30e5ffddb067
name: GCP Audit Logs - Detect Bulk VM Snapshot Deletion
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  
queryPeriod: 15m
triggerThreshold: 0
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.'  
entityMappings:
- entityType: Account
  fieldMappings:
  - identifier: FullName
    columnName: PrincipalEmail
  - identifier: Name
    columnName: AccountName
  - identifier: UPNSuffix
    columnName: AccountUPNSuffix
- entityType: CloudApplication
  fieldMappings:
  - identifier: Name
    columnName: ProjectId
severity: High
tactics:
- Impact
- DefenseEvasion
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Google Cloud Platform Audit Logs/Analytic Rules/GCPBulkVMSnapshotDeletion.yaml