CIS GCP 5.1 (Ensure Cloud Storage buckets are not publicly accessible) requires: Cloud Storage buckets should not grant access to allUsers or allAuthenticatedUsers. This is a critical-severity control.

How does EchelonGraph detect CIS GCP 5.1 violations?

EchelonGraph automatically detects CIS GCP 5.1 violations using scanner rule GCP-STG-001. The scanner checks cloud infrastructure configurations in real-time and flags non-compliant resources.

What audit questions are asked for CIS GCP 5.1?

List all buckets with public IAM bindings (allUsers or allAuthenticatedUsers). Is the Organization Policy constraint storage.publicAccessPrevention enabled? How do you prevent developers from creating public buckets? What data classification is stored in each bucket?

🔷CIS GCP 5.1Rule: GCP-STG-001critical

Ensure Cloud Storage buckets are not publicly accessible

Description

Cloud Storage buckets should not grant access to allUsers or allAuthenticatedUsers.

⚠️ Risk Impact

Publicly accessible buckets are the leading cause of cloud data breaches. Sensitive data (PII, credentials, backups) can be exfiltrated.

🔍 How EchelonGraph Detects This

GCP-STG-001Automated scanner rule

EchelonGraph's Tier 1 Cloud Scanner automatically checks for this condition across all connected Google Cloud accounts. Violations are flagged as critical-severity findings with remediation guidance.

🖥️ Manual Verification

terminal

gsutil iam get gs://BUCKET_NAME | grep -E 'allUsers|allAuthenticatedUsers'

🔧 Remediation

Remove allUsers and allAuthenticatedUsers from bucket IAM. Enable Uniform Bucket-Level Access.

💀 Real-World Attack Scenario

A backend developer created a GCS bucket for temporary file uploads and set it to public for testing. The bucket name followed a predictable pattern (company-uploads-prod). An attacker discovered it through bucket enumeration and downloaded 340,000 customer records including SSNs, payment history, and medical documents.

💰 Cost of Non-Compliance

Capital One 2019: $80M fine + $190M settlement from public S3 bucket. Average public bucket breach cost: $4.45M (IBM 2024). HIPAA penalties for exposed ePHI: $1.5M per violation category per year.

📋 Audit Questions

1.List all buckets with public IAM bindings (allUsers or allAuthenticatedUsers).
2.Is the Organization Policy constraint storage.publicAccessPrevention enabled?
3.How do you prevent developers from creating public buckets?
4.What data classification is stored in each bucket?

🎯 MITRE ATT&CK Mapping

T1530 — Data from Cloud StorageT1119 — Automated Collection

🏗️ Infrastructure as Code Fix

main.tf

resource "google_storage_bucket" "secure" {
  name                        = "${var.project_id}-data"
  location                    = var.region
  uniform_bucket_level_access = true
  public_access_prevention    = "enforced"
}

⚡ Common Pitfalls

⛔Using ACLs instead of IAM (ACLs can inadvertently grant public access)
⛔Not enabling the organization-level public access prevention policy
⛔Setting buckets to 'allAuthenticatedUsers' thinking it means 'all my users' (it means all Google accounts)

📈 Business Value

Preventing public bucket exposure eliminates the #1 cloud data breach vector. A single public bucket can expose your entire customer database. This control is table-stakes for any compliance certification.

⏱️ Effort Estimate

Manual

2-4 hours to audit all buckets across all projects

With EchelonGraph

EchelonGraph detects public buckets across all projects in <60 seconds

🔗 Cross-Framework References

SOC2-CC6.1ISO27001-A.8.2.3GDPR-Art32HIPAA-164.312(a)(1)

Automate CIS GCP 5.1 compliance

EchelonGraph continuously monitors this control across all your cloud accounts.

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