gcp-audit-logs

name	gcp-audit-logs
description	Configure GCP Cloud Audit Logs for compliance. Set up log routing and BigQuery analysis. Use when auditing GCP activity.
license	MIT
metadata	{"author":"devops-skills","version":"1.0"}

GCP Audit Logs

Audit GCP activity with Cloud Audit Logs for compliance, security investigation, and operational monitoring.

When to Use

• Enabling organization-wide audit logging across GCP projects
• Meeting compliance requirements for SOC 2, HIPAA, PCI DSS, or FedRAMP
• Investigating unauthorized access or suspicious API activity
• Setting up alerting on administrative and data access events
• Exporting logs to BigQuery for long-term analysis and reporting

Audit Log Types

log_types:
  admin_activity:
    description: API calls that modify resource configuration or metadata
    enabled: Always (cannot be disabled)
    retention: 400 days (default)
    cost: No charge
    examples:
      - Creating or deleting VM instances
      - Changing IAM policies
      - Modifying firewall rules

  data_access:
    description: API calls that read resource configuration, metadata, or user data
    enabled: Must be explicitly enabled (except BigQuery)
    retention: 30 days (default)
    cost: Can be significant at high volume
    subtypes:
      ADMIN_READ: Read resource configuration/metadata
      DATA_READ: Read user-provided data
      DATA_WRITE: Write user-provided data

  system_event:
    description: Actions performed by GCP systems on behalf of resources
    enabled: Always (cannot be disabled)
    retention: 400 days (default)
    cost: No charge
    examples:
      - Live migration of VM instances
      - Automatic scaling events

  policy_denied:
    description: Actions denied by VPC Service Controls or organization policies
    enabled: Always (cannot be disabled)
    retention: 400 days (default)
    cost: No charge

Enable Data Access Logs for an Organization

# Get current org IAM policy
gcloud organizations get-iam-policy ORG_ID --format=json > org-policy.json

# Add audit config to org-policy.json:
# {
#   "auditConfigs": [
#     {
#       "service": "allServices",
#       "auditLogConfigs": [
#         {"logType": "ADMIN_READ"},
#         {"logType": "DATA_READ"},
#         {"logType": "DATA_WRITE"}
#       ]
#     }
#   ],
#   ...existing bindings...
# }

# Apply the updated policy
gcloud organizations set-iam-policy ORG_ID org-policy.json

# Enable data access logs for specific services at project level
gcloud projects get-iam-policy PROJECT_ID --format=json > project-policy.json

# Example: enable only for Cloud Storage and BigQuery
# {
#   "auditConfigs": [
#     {
#       "service": "storage.googleapis.com",
#       "auditLogConfigs": [
#         {"logType": "DATA_READ"},
#         {"logType": "DATA_WRITE"}
#       ]
#     },
#     {
#       "service": "bigquery.googleapis.com",
#       "auditLogConfigs": [
#         {"logType": "DATA_READ"},
#         {"logType": "DATA_WRITE"}
#       ]
#     }
#   ]
# }

gcloud projects set-iam-policy PROJECT_ID project-policy.json

Configure Log Sinks for Export

# Create BigQuery dataset for audit log export
bq mk --dataset \
  --description "Audit log export" \
  --default_table_expiration 0 \
  --location US \
  PROJECT_ID:audit_logs

# Create organization-level log sink to BigQuery
gcloud logging sinks create org-audit-bigquery \
  bigquery.googleapis.com/projects/PROJECT_ID/datasets/audit_logs \
  --organization=ORG_ID \
  --include-children \
  --log-filter='logName:"cloudaudit.googleapis.com"'

# Get the sink writer identity and grant BigQuery access
SINK_SA=$(gcloud logging sinks describe org-audit-bigquery \
  --organization=ORG_ID --format='value(writerIdentity)')

bq add-iam-policy-binding \
  --member="$SINK_SA" \
  --role="roles/bigquery.dataEditor" \
  PROJECT_ID:audit_logs

# Create Cloud Storage sink for long-term archive
gsutil mb -l US -b on gs://org-audit-logs-archive
gsutil retention set 7y gs://org-audit-logs-archive

gcloud logging sinks create org-audit-storage \
  storage.googleapis.com/org-audit-logs-archive \
  --organization=ORG_ID \
  --include-children \
  --log-filter='logName:"cloudaudit.googleapis.com"'

STORAGE_SA=$(gcloud logging sinks describe org-audit-storage \
  --organization=ORG_ID --format='value(writerIdentity)')

gsutil iam ch "$STORAGE_SA:objectCreator" gs://org-audit-logs-archive

# Create Pub/Sub sink for real-time streaming to SIEM
gcloud pubsub topics create audit-log-stream

gcloud logging sinks create org-audit-pubsub \
  pubsub.googleapis.com/projects/PROJECT_ID/topics/audit-log-stream \
  --organization=ORG_ID \
  --include-children \
  --log-filter='logName:"cloudaudit.googleapis.com" AND (protoPayload.methodName:"delete" OR protoPayload.methodName:"setIamPolicy" OR severity>=WARNING)'

PUBSUB_SA=$(gcloud logging sinks describe org-audit-pubsub \
  --organization=ORG_ID --format='value(writerIdentity)')

gcloud pubsub topics add-iam-policy-binding audit-log-stream \
  --member="$PUBSUB_SA" \
  --role="roles/pubsub.publisher"

Logging Queries (Cloud Logging Explorer)

# View admin activity logs for the last 24 hours
gcloud logging read 'logName:"cloudaudit.googleapis.com/activity"
  AND timestamp>="2024-01-01T00:00:00Z"' \
  --project=PROJECT_ID \
  --format=json \
  --limit=100

# Find IAM policy changes
gcloud logging read 'logName:"cloudaudit.googleapis.com/activity"
  AND protoPayload.methodName="SetIamPolicy"' \
  --project=PROJECT_ID \
  --freshness=7d

# Find resource deletions
gcloud logging read 'logName:"cloudaudit.googleapis.com/activity"
  AND protoPayload.methodName=~"delete"
  AND severity>=NOTICE' \
  --project=PROJECT_ID \
  --freshness=7d

# Data access audit log entries
gcloud logging read 'logName:"cloudaudit.googleapis.com/data_access"
  AND protoPayload.serviceName="storage.googleapis.com"
  AND protoPayload.methodName="storage.objects.get"' \
  --project=PROJECT_ID \
  --freshness=24h

# Failed authorization attempts
gcloud logging read 'logName:"cloudaudit.googleapis.com/policy"' \
  --project=PROJECT_ID \
  --freshness=7d

BigQuery Analysis Queries

-- All destructive operations in the last 30 days
SELECT
  timestamp,
  protopayload_auditlog.authenticationInfo.principalEmail AS principal,
  protopayload_auditlog.methodName AS method,
  protopayload_auditlog.resourceName AS resource,
  resource.labels.project_id AS project,
  protopayload_auditlog.status.code AS status_code,
  protopayload_auditlog.status.message AS status_message
FROM `project.audit_logs.cloudaudit_googleapis_com_activity_*`
WHERE _TABLE_SUFFIX >= FORMAT_DATE('%Y%m%d', DATE_SUB(CURRENT_DATE(), INTERVAL 30 DAY))
  AND protopayload_auditlog.methodName LIKE '%delete%'
ORDER BY timestamp DESC
LIMIT 500;

-- IAM policy changes across the organization
SELECT
  timestamp,
  protopayload_auditlog.authenticationInfo.principalEmail AS changed_by,
  resource.labels.project_id AS project,
  protopayload_auditlog.resourceName AS resource,
  protopayload_auditlog.servicedata_v1_iam.policyDelta.bindingDeltas
FROM `project.audit_logs.cloudaudit_googleapis_com_activity_*`
WHERE _TABLE_SUFFIX >= FORMAT_DATE('%Y%m%d', DATE_SUB(CURRENT_DATE(), INTERVAL 30 DAY))
  AND protopayload_auditlog.methodName  
   ;



  protopayload_auditlog.authenticationInfo.principalEmail  principal,
  ()  action_count,
  ( protopayload_auditlog.methodName)  unique_methods,
  ( protopayload_auditlog.requestMetadata.callerIp)  unique_ips,
  ()  first_activity,
  ()  last_activity
 `project.audit_logs.cloudaudit_googleapis_com_activity_`
 _TABLE_SUFFIX  FORMAT_DATE(, DATE_SUB((),   ))
  principal
  action_count 
LIMIT ;



  ,
  protopayload_auditlog.authenticationInfo.principalEmail  created_by,
  protopayload_auditlog.resourceName  service_account,
  protopayload_auditlog.requestMetadata.callerIp  source_ip
 `project.audit_logs.cloudaudit_googleapis_com_activity_`
 _TABLE_SUFFIX  FORMAT_DATE(, DATE_SUB((),   ))
   protopayload_auditlog.methodName  
   ;



  ,
  protopayload_auditlog.authenticationInfo.principalEmail  accessor,
  protopayload_auditlog.resourceName  object_path,
  protopayload_auditlog.methodName  access_type,
  protopayload_auditlog.requestMetadata.callerIp  source_ip
 `project.audit_logs.cloudaudit_googleapis_com_data_access_`
 _TABLE_SUFFIX  FORMAT_DATE(, DATE_SUB((),   ))
   protopayload_auditlog.resourceName  
   
LIMIT ;



  ,
  protopayload_auditlog.authenticationInfo.principalEmail  principal,
  protopayload_auditlog.methodName  ,
  protopayload_auditlog.status.code  error_code,
  protopayload_auditlog.status.message  error_message,
  protopayload_auditlog.requestMetadata.callerIp  source_ip
 `project.audit_logs.cloudaudit_googleapis_com_activity_`
 _TABLE_SUFFIX  FORMAT_DATE(, DATE_SUB((),   ))
   protopayload_auditlog.status.code  
   
LIMIT ;

Alerting Policies

# Alert on service account key creation
gcloud alpha monitoring policies create \
  --display-name="SA Key Created" \
  --condition-display-name="Service Account Key Creation" \
  --condition-filter='resource.type="audited_resource" AND protoPayload.methodName="google.iam.admin.v1.CreateServiceAccountKey"' \
  --condition-threshold-value=0 \
  --condition-threshold-comparison=COMPARISON_GT \
  --condition-threshold-duration=0s \
  --notification-channels=projects/PROJECT_ID/notificationChannels/CHANNEL_ID \
  --combiner=OR

# Create a log-based metric for IAM changes
gcloud logging metrics create iam-policy-changes \
  --description="Count of IAM policy changes" \
  --log-filter='logName:"cloudaudit.googleapis.com/activity" AND protoPayload.methodName="SetIamPolicy"'

# Create alerting policy using the log-based metric
gcloud alpha monitoring policies create \
  --display-name="IAM Policy Changes" \
  --condition-display-name="IAM Changes Detected" \
  --condition-filter='metric.type="logging.googleapis.com/user/iam-policy-changes"' \
  --condition-threshold-value=0 \
  --condition-threshold-comparison=COMPARISON_GT \
  --condition-threshold-duration=0s \
  --notification-channels=projects/PROJECT_ID/notificationChannels/CHANNEL_ID

# Create log-based metric for firewall changes
gcloud logging metrics create firewall-rule-changes \
  --description="Count of firewall rule changes" \
  --log-filter='logName:"cloudaudit.googleapis.com/activity"
    AND (protoPayload.methodName="v1.compute.firewalls.insert"
    OR protoPayload.methodName="v1.compute.firewalls.delete"
    OR protoPayload.methodName="v1.compute.firewalls.patch")'

# Create log-based metric for VPC network changes
gcloud logging metrics create vpc-network-changes \
  --description="Count of VPC network changes" \
  --log-filter='logName:"cloudaudit.googleapis.com/activity"
    AND resource.type="gce_network"
    AND (protoPayload.methodName=~"insert$" OR protoPayload.methodName=~"delete$")'

Terraform Configuration

# Organization-level audit log sink to BigQuery
resource "google_logging_organization_sink" "audit_bigquery" {
  name             = "org-audit-bigquery"
  org_id           = var.org_id
  destination      = "bigquery.googleapis.com/projects/${var.project_id}/datasets/${google_bigquery_dataset.audit_logs.dataset_id}"
  filter           = "logName:\"cloudaudit.googleapis.com\""
  include_children = true

  bigquery_options {
    use_partitioned_tables = true
  }
}

resource "google_bigquery_dataset" "audit_logs" {
  dataset_id    = "audit_logs"
  project       = var.project_id
  location      = "US"
  description   = "Organization audit log export"

  default_table_expiration_ms = null  # No auto-expiry

  access {
    role          = "WRITER"
    user_by_email = google_logging_organization_sink.audit_bigquery.writer_identity
  }

  access {
    role          = "READER"
    group_by_email = "[e-mail]"
  }
}

# Retention bucket with bucket lock
resource "google_storage_bucket" "audit_archive" {
  name          = "org-audit-logs-archive"
  location      = "US"
  force_destroy = false
  project       = var.project_id

  uniform_bucket_level_access = true

  retention_policy {
    is_locked        = true
    retention_period = 220752000  # 7 years in seconds
  }

  lifecycle_rule {
    condition {
      age = 90
    }
    action {
      type          = "SetStorageClass"
      storage_class = "COLDLINE"
    }
  }
}

# Log-based alerting
resource "google_logging_metric" "iam_changes" {
  name    = "iam-policy-changes"
  project = var.project_id
  filter  = "logName:\"cloudaudit.googleapis.com/activity\" AND protoPayload.methodName=\"SetIamPolicy\""

  metric_descriptor {
    metric_kind = "DELTA"
    value_type  = "INT64"
  }
}

resource "google_monitoring_alert_policy" "iam_changes" {
  display_name = "IAM Policy Changes Detected"
  project      = var.project_id
  combiner     = "OR"

  conditions {
    display_name = "IAM policy change count"
    condition_threshold {
      filter          = "metric.type=\"logging.googleapis.com/user/iam-policy-changes\" AND resource.type=\"global\""
      comparison      = "COMPARISON_GT"
      threshold_value = 0
      duration        = "0s"
    }
  }

  notification_channels = [var.notification_channel_id]
}

Setup Checklist

gcp_audit_logs_checklist:
  log_enablement:
    - [ ] Admin activity logs verified active (always on)
    - [ ] Data access logs enabled for sensitive services
    - [ ] Data access exemptions configured to exclude high-volume, low-risk operations
    - [ ] System event logs verified active (always on)

  log_routing:
    - [ ] Organization-level sink to BigQuery for analysis
    - [ ] Organization-level sink to Cloud Storage for long-term archive
    - [ ] Pub/Sub sink for      
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Best Practices

• Enable data access logs selectively on sensitive services to control cost and volume
• Use organization-level sinks with include-children to capture all projects automatically
• Export to BigQuery with partitioned tables for efficient querying over large time ranges
• Archive to Cloud Storage with bucket lock and retention policies for immutable long-term storage
• Create log-based metrics and alerting policies for high-severity events
• Stream critical audit events via Pub/Sub to SIEM for real-time correlation
• Apply exemptions to exclude high-volume read-only service accounts from data access logs
• Restrict access to audit log sinks and destinations with least-privilege IAM bindings
• Regularly run BigQuery analysis queries to detect anomalous patterns and generate compliance reports
• Monitor log sink health and delivery latency to ensure continuous audit coverage