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Ensure VMs are not publicly accessible

Cyscale looks for virtual machines reachable from the internet on administration ports (22, 3389). To reduce the risk of data breaches, configure the security groups/firewalls to allow access only from specific sources or re-consider whether you really need SSH/RDP access.

Category

Controls

Medium

Applies to

Alibaba CloudAWSGoogle CloudMicrosoft Azure

Coverage

null controls, 3 queries

Asset types

1 covered

Overview

Cyscale looks for virtual machines reachable from the internet on administration ports (22, 3389). To reduce the risk of data breaches, configure the security groups/firewalls to allow access only from specific sources or re-consider whether you really need SSH/RDP access.

Remediation guidance

Azure

Disable direct SSH access to your Azure Virtual Machines from the Internet. After direct SSH access from the Internet is disabled, you have other options you can use to access these virtual machines for remote management:

  • Point-to-site VPN
  • Site-to-site VPN
  • ExpressRoute

By default, SSH access from the internet is not enabled.

For more details check Azure specific control for this issue: azure-1-3-0-networking-2.

References

  1. Azure best practices for network security
  2. Security Control V2: Network Security

AWS

Check your EC2 security groups for inbound rules that allow unrestricted access (i.e. 0.0.0.0/0 or ::/0) to TCP port 22. Restrict access to only those IP addresses that require it, in order to implement the principle of least privilege and reduce the possibility of a breach.

References

  1. Security groups: inbound and outbound rules

Alibaba

Similar with Azure, you have to check your Elastic Compute Services (ECS) security groups for inbound rules that allow unrestricted access (i.e. 0.0.0.0/0 or ::/0) to TCP port 22.

For more details check the Alibaba Specific control for this issue: cis-alibaba-1-0-0-networking-2.

References

  1. Security groups for different use cases

Google Cloud

Make sure that you don't have any Firewall Rule that allow unrestricted access (i.e. 0.0.0.0/0 or ::/0) to TCP port 22 for any of your VPC Networks.

For more details check the Google Cloud specific control for this issue: gcp-networking-3.

References

  1. VPC firewall rules

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.

Publicly Accessible VMs for AWS/Alibaba

Connectors

Alibaba CloudAWS

Covered asset types

VM

Expected check: eq []

{
  vms(
    where: {
      publicIpAddress_NOT: null
      securityGroups_SOME: {
        rules_SOME: {
          direction: "Inbound"
          action: "Allow"
          AND: [
            {
              OR: [
                { sources_INCLUDES: "cidr:0.0.0.0/0" }
                { sources_INCLUDES: "cidr:::/0" }
              ]
            }
            {
              OR: [
                { destFromPort_LTE: 22, destToPort_GTE: 22 }
                { destFromPort_LTE: 3389, destToPort_GTE: 3389 }
              ]
            }
          ]
        }
      }
    }
  ) {
    ...AssetFragment
  }
}
Publicly Accessible VMs for Azure

Connectors

Microsoft Azure

Covered asset types

VM

Expected check: eq []

{
  vms(
    where: {
      networkInterfaces_SOME: {
        publicIp_NOT: null
        securityGroups_SOME: {
          rules_SOME: {
            direction: "Inbound"
            action: "Allow"
            AND: [
              {
                OR: [
                  { sources_INCLUDES: "cidr:0.0.0.0/0" }
                  { sources_INCLUDES: "cidr:::/0" }
                  { sources_INCLUDES: "tag:Internet" }
                  { sources: [] }
                ]
              }
              {
                OR: [
                  { destFromPort_LTE: 22, destToPort_GTE: 22 }
                  { destFromPort_LTE: 3389, destToPort_GTE: 3389 }
                ]
              }
            ]
          }
        }
      }
    }
  ) {
    ...AssetFragment
  }
}
Publicly Accessible VMs for Google Cloud

Connectors

Google Cloud

Covered asset types

VM

Expected check: eq []

{
  vms(
    where: {
      networkInterfaces_SOME: { NOT: { accessConfigs_SOME: null } }
      NOT: { name_STARTS_WITH: "gke-" }
      firewalls_SOME: {
        rules_SOME: {
          direction: "Inbound"
          AND: [
            {
              OR: [
                { sources_INCLUDES: "cidr:0.0.0.0/0" }
                { sources_INCLUDES: "cidr:::/0" }
              ]
            }
            {
              OR: [
                { destFromPort_LTE: 22, destToPort_GTE: 22 }
                { destFromPort_LTE: 3389, destToPort_GTE: 3389 }
              ]
            }
          ]
        }
      }
    }
  ) {
    ...AssetFragment
  }
}
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