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Ensure buckets are not accessible from VMs with open management ports

### Overview

Category

Controls

Medium

Applies to

Alibaba CloudAWSGoogle CloudMicrosoft Azure

Coverage

null controls, 4 queries

Asset types

2 covered

Overview

Overview

Cyscale looks for buckets that are accessible from virtual machines with open management ports.

Remediation guidance

Remediation strategy

  1. Close public management ports on VMs.
  2. Restrict storage access permissions of VM-attached identities.

AWS

aws ec2 revoke-security-group-ingress --group-id <sg-id> --protocol tcp --port 22 --cidr 0.0.0.0/0
aws ec2 revoke-security-group-ingress --group-id <sg-id> --protocol tcp --port 3389 --cidr 0.0.0.0/0

GCP

gcloud compute firewall-rules update <rule-name> --source-ranges=<trusted-cidr>

Azure

az network nsg rule update --resource-group <rg> --nsg-name <nsg> --name <rule> --source-address-prefixes <trusted-cidr>

References

  • https://docs.aws.amazon.com/vpc/latest/userguide/vpc-security-groups.html
  • https://cloud.google.com/firewall/docs/using-firewalls
  • https://learn.microsoft.com/en-us/azure/virtual-network/network-security-groups-overview

Multiple Remediation Paths

AWS

SERVICE-WIDE (RECOMMENDED when many resources are affected): Deploy centralized guardrails and remediation using AWS Config Conformance Packs and (if applicable) AWS Organizations SCPs.

aws configservice put-organization-conformance-pack --organization-conformance-pack-name <pack-name> --template-s3-uri s3://<bucket>/<template>.yaml

ASSET-LEVEL: Apply the resource-specific remediation steps above to only the affected assets.

PREVENTIVE: Add CI/CD policy checks (CloudFormation/Terraform validation) before deployment to prevent recurrence.

Google Cloud

SERVICE-WIDE (RECOMMENDED when many resources are affected): Enforce Organization Policies at org/folder level so new resources inherit secure defaults.

gcloud org-policies set-policy policy.yaml

ASSET-LEVEL: Use the product-specific remediation steps above for only the impacted project/resources.

PREVENTIVE: Use org policy constraints/custom constraints and enforce checks in deployment pipelines.

Azure

SERVICE-WIDE (RECOMMENDED when many resources are affected): Assign Azure Policy initiatives at management group/subscription scope and trigger remediation tasks.

az policy assignment create --name <assignment-name> --scope /subscriptions/<subscription-id> --policy-set-definition <initiative-id>
az policy remediation create --name <remediation-name> --policy-assignment <assignment-id>

ASSET-LEVEL: Apply the resource-specific remediation steps above to the listed non-compliant resources.

PREVENTIVE: Embed Azure Policy checks into landing zones and IaC workflows to block or auto-remediate drift.

References for Service-Wide Patterns

  • AWS Config Conformance Packs: https://docs.aws.amazon.com/config/latest/developerguide/conformance-packs.html
  • AWS Organizations SCP examples: https://docs.aws.amazon.com/organizations/latest/userguide/orgs_manage_policies_scps_examples.html
  • GCP Organization Policy overview: https://cloud.google.com/resource-manager/docs/organization-policy/overview
  • GCP Organization policy constraints catalog: https://cloud.google.com/resource-manager/docs/organization-policy/org-policy-constraints
  • gcloud org-policies: https://cloud.google.com/sdk/gcloud/reference/org-policies
  • Azure Policy overview: https://learn.microsoft.com/en-us/azure/governance/policy/overview
  • Azure Policy remediation: https://learn.microsoft.com/en-us/azure/governance/policy/how-to/remediate-resources
  • Azure Policy initiative structure: https://learn.microsoft.com/en-us/azure/governance/policy/concepts/initiative-definition-structure

Operational Rollout Workflow

Use this sequence to reduce risk and avoid repeated drift.

1. Contain at Service-Wide Scope First (Recommended)

  • AWS: deploy/adjust organization conformance packs and policy guardrails.
aws configservice put-organization-conformance-pack --organization-conformance-pack-name <pack-name> --template-s3-uri s3://<bucket>/<template>.yaml
  • Google Cloud: apply organization policy constraints at org/folder scope.
gcloud org-policies set-policy policy.yaml
  • Azure: assign policy initiatives at management group/subscription scope and run remediation tasks.
az policy assignment create --name <assignment-name> --scope /subscriptions/<subscription-id> --policy-set-definition <initiative-id>
az policy remediation create --name <remediation-name> --policy-assignment <assignment-id>

2. Remediate Existing Affected Assets

  • Execute the control-specific Console/CLI steps documented above for each flagged resource.
  • Prioritize internet-exposed and production assets first.

3. Validate and Prevent Recurrence

  • Re-scan after each remediation batch.
  • Track exceptions with owner and expiry date.
  • Add preventive checks in IaC/CI pipelines.

Query logic

These are the stored checks tied to this control.

AWS Buckets accessible from VMs with open management ports

Connectors

AWS

Covered asset types

Bucket

Expected check: eq []

{
  accessibleBucketsFromAWSVMs {...AssetFragment}
}
Google Cloud Buckets accessible from VMs with open management port

Connectors

Google Cloud

Covered asset types

Bucket

Expected check: eq []

{
  accessibleBucketsFromGCPVMs {...AssetFragment}
}
Azure Blob Accessible from vms with open management port

Connectors

Microsoft Azure

Covered asset types

BlobContainer

Expected check: eq []

{
  accessibleBlobContainersFromAzureVMs {...AssetFragment}
}
Alibaba Buckets accessible from VMs with open management port

Connectors

Alibaba Cloud

Covered asset types

Bucket

Expected check: eq []

{
  accessibleBucketsFromAlibabaVMs {...AssetFragment}
}
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