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πŸ›‘οΈ Azure VM Scale Set Instance allows public access to RPC port🟒

  • Contextual name: πŸ›‘οΈ Instance allows public access to RPC port🟒
  • ID: /ce/ca/azure/vm-scale-set/instance-allows-unrestricted-rpc-traffic
  • Tags:
  • Policy Type: COMPLIANCE_POLICY
  • Policy Categories: SECURITY

Stats​

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Logic​

Similar Policies​

  • Internal: dec-x-36226bed

Similar Internal Rules​

RulePoliciesFlags
βœ‰οΈ dec-x-36226bed3

Description​

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Description​

Ensure that Azure VM Scale set Instances are not configured to allow unrestricted inbound access to the Remote Procedure Call (RPC) port (TCP 135). Network Security Group (NSG) rules should explicitly restrict inbound traffic to this port to only trusted IP ranges to enhance security posture and prevent unauthorized communication.

Rationale​

RPC (port 135) is frequently targeted by threat actors due to its role in enabling remote administration and inter-process communication between distributed systems. Unrestricted access to this port can lead to unauthorized system access, remote code execution, and lateral movement across the network. Restricting inbound RPC traffic to known, trusted sources helps mitigate risks associated with protocol exploitation, unauthorized data exposure, and the propagation of malware within the environment.

Impact​

Before implementing restrictions, validate that all dependent applications and services relying on RPC functionality are identified and accounted for. Failure to properly evaluate dependencies may result in service disruptions or degraded functionality.

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Remediation​

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Remediation​

Modify or Remove Insecure NSG Rule​

Review the security rules associated with the relevant Network Security Group (NSG) and determine whether they are required. Take appropriate action based on necessity and scope:

  • If the rule is not required: Remove the rule entirely.

  • If the rule is required but overly permissive: Update the rule to narrowly scope access, restricting the source IP range to only what is strictly necessary.

Azure CLI​

  1. Delete the rule:

    az network nsg rule delete \
      --resource-group {{resource-group-name}} \
      --nsg-name {{nsg-name}} \
      --name {{rule-name}}

  2. Restrict the rule:

    az network nsg rule update \
        --resource-group {{resource-group-name}} \
        --nsg-name {{nsg-name}} \
        --name {{rule-name}} \
        --source-address-prefixes {{trusted-cidr}}

    Replace placeholders with the appropriate values. Use space-separated values for multiple source prefixes or destination ports (e.g., --source-address-prefixes "1.2.3.4/32 5.6.7.8/32").

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policy.yaml​

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Linked Framework Sections​

SectionSub SectionsInternal RulesPoliciesFlagsCompliance
πŸ’Ό APRA CPG 234 β†’ πŸ’Ό 36f network design β€” to ensure authorised network traffic flows and to reduce the impact of security compromises;76107no data
πŸ’Ό APRA CPG 234 β†’ πŸ’Ό 45 An understanding of plausible worst case scenarios can help regulated entities identify and implement additional controls to prevent or reduce the impact of such scenarios. One example is malware that infects computers and encrypts data, both on the infected computer and any connected storage, including (corporate) networks and cloud storage. Such attacks reinforce the importance of protecting the backup environment in the event that the production environment is compromised. Common techniques to achieve this include network segmentation, highly restricted and segregated access controls and network traffic flow restrictions.83115no data
πŸ’Ό Cloudaware Framework β†’ πŸ’Ό Network Exposure137no data
πŸ’Ό FedRAMP High Security Controls β†’ πŸ’Ό AC-4(21) Physical or Logical Separation of Information Flows (M)(H)18141no data
πŸ’Ό FedRAMP Moderate Security Controls β†’ πŸ’Ό AC-4(21) Physical or Logical Separation of Information Flows (M)(H)141no data
πŸ’Ό ISO/IEC 27001:2013 β†’ πŸ’Ό A.9.1.2 Access to networks and network services2767no data
πŸ’Ό ISO/IEC 27001:2013 β†’ πŸ’Ό A.9.4.1 Information access restriction4992no data
πŸ’Ό NIST CSF v1.1 β†’ πŸ’Ό PR.AC-4: Access permissions and authorizations are managed, incorporating the principles of least privilege and separation of duties48127no data
πŸ’Ό NIST CSF v1.1 β†’ πŸ’Ό PR.DS-5: Protections against data leaks are implemented89152no data
πŸ’Ό NIST CSF v1.1 β†’ πŸ’Ό PR.PT-3: The principle of least functionality is incorporated by configuring systems to provide only essential capabilities3179no data
πŸ’Ό NIST CSF v2.0 β†’ πŸ’Ό PR.AA-05: Access permissions, entitlements, and authorizations are defined in a policy, managed, enforced, and reviewed, and incorporate the principles of least privilege and separation of duties199no data
πŸ’Ό NIST CSF v2.0 β†’ πŸ’Ό PR.DS-01: The confidentiality, integrity, and availability of data-at-rest are protected248no data
πŸ’Ό NIST CSF v2.0 β†’ πŸ’Ό PR.DS-02: The confidentiality, integrity, and availability of data-in-transit are protected219no data
πŸ’Ό NIST CSF v2.0 β†’ πŸ’Ό PR.DS-10: The confidentiality, integrity, and availability of data-in-use are protected249no data
πŸ’Ό NIST SP 800-53 Revision 5 β†’ πŸ’Ό AC-4(21) Information Flow Enforcement _ Physical or Logical Separation of Information Flows83141no data
πŸ’Ό PCI DSS v3.2.1 β†’ πŸ’Ό 1.1 Establish and implement firewall and router configuration standards71110no data
πŸ’Ό PCI DSS v3.2.1 β†’ πŸ’Ό 1.1.6 Documentation of business justification and approval for use of all services, protocols, and ports allowed, including documentation of security features implemented for those protocols considered to be insecure.195no data
πŸ’Ό PCI DSS v3.2.1 β†’ πŸ’Ό 1.2.1 Restrict inbound and outbound traffic to that which is necessary for the cardholder data environment, and specifically deny all other traffic.16111no data
πŸ’Ό PCI DSS v3.2.1 β†’ πŸ’Ό 1.3 Prohibit direct public access between the Internet and any system component in the cardholder data environment.712113no data
πŸ’Ό PCI DSS v3.2.1 β†’ πŸ’Ό 1.3.1 Implement a DMZ to limit inbound traffic to only system components that provide authorized publicly accessible services, protocols, and ports.10100no data
πŸ’Ό PCI DSS v3.2.1 β†’ πŸ’Ό 1.3.2 Limit inbound Internet traffic to IP addresses within the DMZ.100no data
πŸ’Ό PCI DSS v3.2.1 β†’ πŸ’Ό 1.3.5 Permit only β€œestablished” connections into the network.100no data
πŸ’Ό PCI DSS v3.2.1 β†’ πŸ’Ό 2.2.3 Implement additional security features for any required services, protocols, or daemons that are considered to be insecure.415no data
πŸ’Ό PCI DSS v3.2.1 β†’ πŸ’Ό 2.2.4 Configure system security parameters to prevent misuse.40no data
πŸ’Ό PCI DSS v4.0.1 β†’ πŸ’Ό 1.2.1 Configuration standards for NSC rulesets are defined, implemented, maintained.105no data
πŸ’Ό PCI DSS v4.0.1 β†’ πŸ’Ό 1.2.5 All services, protocols, and ports allowed are identified, approved, and have a defined business need.95no data
πŸ’Ό PCI DSS v4.0.1 β†’ πŸ’Ό 1.2.6 Security features are defined and implemented for all services, protocols, and ports that are in use and considered to be insecure, such that the risk is mitigated.95no data
πŸ’Ό PCI DSS v4.0.1 β†’ πŸ’Ό 1.3.1 Inbound traffic to the CDE is restricted.111no data
πŸ’Ό PCI DSS v4.0.1 β†’ πŸ’Ό 1.3.2 Outbound traffic from the CDE is restricted.111no data
πŸ’Ό PCI DSS v4.0.1 β†’ πŸ’Ό 1.4.1 NSCs are implemented between trusted and untrusted networks.90no data
πŸ’Ό PCI DSS v4.0.1 β†’ πŸ’Ό 1.4.2 Inbound traffic from untrusted networks to trusted networks is restricted.100no data
πŸ’Ό PCI DSS v4.0.1 β†’ πŸ’Ό 2.2.5 If any insecure services, protocols, or daemons are present, business justification is documented.15no data
πŸ’Ό PCI DSS v4.0.1 β†’ πŸ’Ό 2.2.6 System security parameters are configured to prevent misuse.40no data
πŸ’Ό PCI DSS v4.0 β†’ πŸ’Ό 1.2.1 Configuration standards for NSC rulesets are defined, implemented, maintained.62105no data
πŸ’Ό PCI DSS v4.0 β†’ πŸ’Ό 1.2.5 All services, protocols, and ports allowed are identified, approved, and have a defined business need.4795no data
πŸ’Ό PCI DSS v4.0 β†’ πŸ’Ό 1.2.6 Security features are defined and implemented for all services, protocols, and ports that are in use and considered to be insecure, such that the risk is mitigated.2195no data
πŸ’Ό PCI DSS v4.0 β†’ πŸ’Ό 1.3.1 Inbound traffic to the CDE is restricted.31111no data
πŸ’Ό PCI DSS v4.0 β†’ πŸ’Ό 1.3.2 Outbound traffic from the CDE is restricted.111no data
πŸ’Ό PCI DSS v4.0 β†’ πŸ’Ό 1.4.1 NSCs are implemented between trusted and untrusted networks.3190no data
πŸ’Ό PCI DSS v4.0 β†’ πŸ’Ό 1.4.2 Inbound traffic from untrusted networks to trusted networks is restricted.31100no data
πŸ’Ό PCI DSS v4.0 β†’ πŸ’Ό 2.2.5 If any insecure services, protocols, or daemons are present, business justification is documented.15no data
πŸ’Ό PCI DSS v4.0 β†’ πŸ’Ό 2.2.6 System security parameters are configured to prevent misuse.2340no data
πŸ’Ό SOC 2 β†’ πŸ’Ό CC6.1-7 Restricts Access to Information Assets1867no data
πŸ’Ό SOC 2 β†’ πŸ’Ό CC6.6-1 Restricts Access2162no data
πŸ’Ό UK Cyber Essentials β†’ πŸ’Ό 1.2 Prevent access to the administrative interface from the internet85119no data