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📝 AWS EC2 Security Group allows unrestricted DNS traffic 🟢

  • Contextual name: 📝 Security Group allows unrestricted DNS traffic 🟢
  • ID: /ce/ca/aws/ec2/security-group-allows-unrestricted-dns-traffic
  • Located in: 📁 AWS EC2

Flags​

Our Metadata​

  • Policy Type: COMPLIANCE_POLICY
  • Policy Category:
    • SECURITY

Similar Policies​

Similar Internal Rules​

RulePoliciesFlags
✉️ dec-z-dbeeed9f1
✉️ dec-z-f778950c1

Logic​

Description​

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Description​

AWS EC2 Security Groups should not allow unrestricted DNS traffic to avoid exposure to security vulnerabilities. Security group rules should be configured to limit DNS traffic (UDP port 53) to trusted IP ranges, such as internal networks or approved DNS servers, reducing the risk of misuse or attacks such as DNS amplification.

Rationale​

Restricting DNS traffic prevents unauthorized use of EC2 instances for malicious activities, such as DNS tunneling or participating in amplification attacks. By limiting DNS access to trusted sources, you ensure only authorized clients and servers can interact, reducing the surface area for potential exploits.

Impact​

Implementing restrictions might cause service interruptions if legitimate applications are not properly configured to use allowed DNS servers, making it essential to validate and update configurations thoroughly during remediation.

Audit​

This policy marks an EC2 Security Group as INCOMPLIANT if it contains a rule that meets all the following conditions:

... see more

Remediation​

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Remediation​

From Command Line​

  1. Run the following command to remove or modify the unrestricted rule for DNS access:
aws ec2 revoke-security-group-ingress \
--region {{region-name}} \
--group-id {{security-group-id}} \
--protocol {{protocol}} \
--port 53 \
--cidr {{0.0.0.0/0 or ::/0}}

  • Optionally, run the authorise-security-group-ingress command to create a new rule, specifying a trusted CIDR range instead of 0.0.0.0/0.

  1. Confirm the changes by describing the security group again and ensuring the unrestricted access rule has been removed or appropriately restricted:
aws ec2 describe-security-groups \
--region {{region-name}} \
--group-ids {{security-group-id}} \
--query 'SecurityGroups[*].IpPermissions[?FromPort==`53`].{CIDR:IpRanges[*].CidrIp,Port:FromPort}'
  1. Test the functionality of services that rely on DNS to ensure that they operate correctly with the updated security group rules.

policy.yaml​

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Linked Framework Sections​

SectionSub SectionsInternal RulesPoliciesFlags
💼 APRA CPG 234 → 💼 36f network design — to ensure authorised network traffic flows and to reduce the impact of security compromises;2628
💼 APRA CPG 234 → 💼 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.3235
💼 Cloudaware Framework → 💼 Threat Protection25
💼 FedRAMP High Security Controls → 💼 AC-3 Access Enforcement (L)(M)(H)3546
💼 FedRAMP High Security Controls → 💼 AC-4(21) Physical or Logical Separation of Information Flows (M)(H)1138
💼 FedRAMP High Security Controls → 💼 CM-7(1) Periodic Review (M)(H)1111
💼 FedRAMP Low Security Controls → 💼 AC-3 Access Enforcement (L)(M)(H)46
💼 FedRAMP Moderate Security Controls → 💼 AC-3 Access Enforcement (L)(M)(H)46
💼 FedRAMP Moderate Security Controls → 💼 AC-4(21) Physical or Logical Separation of Information Flows (M)(H)38
💼 FedRAMP Moderate Security Controls → 💼 CM-7(1) Periodic Review (M)(H)11
💼 ISO/IEC 27001:2013 → 💼 A.9.1.2 Access to networks and network services1718
💼 NIST CSF v1.1 → 💼 PR.AC-4: Access permissions and authorizations are managed, incorporating the principles of least privilege and separation of duties1534
💼 NIST CSF v1.1 → 💼 PR.DS-5: Protections against data leaks are implemented4150
💼 NIST CSF v1.1 → 💼 PR.PT-3: The principle of least functionality is incorporated by configuring systems to provide only essential capabilities2125
💼 NIST CSF v2.0 → 💼 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 duties57
💼 NIST CSF v2.0 → 💼 PR.DS-01: The confidentiality, integrity, and availability of data-at-rest are protected81
💼 NIST CSF v2.0 → 💼 PR.DS-02: The confidentiality, integrity, and availability of data-in-transit are protected68
💼 NIST CSF v2.0 → 💼 PR.DS-10: The confidentiality, integrity, and availability of data-in-use are protected66
💼 NIST SP 800-53 Revision 5 → 💼 AC-4(21) Information Flow Enforcement _ Physical or Logical Separation of Information Flows3338
💼 PCI DSS v3.2.1 → 💼 1.2.1 Restrict inbound and outbound traffic to that which is necessary for the cardholder data environment, and specifically deny all other traffic.1014
💼 PCI DSS v4.0.1 → 💼 1.3.1 Inbound traffic to the CDE is restricted.14
💼 PCI DSS v4.0.1 → 💼 1.3.2 Outbound traffic from the CDE is restricted.14
💼 PCI DSS v4.0 → 💼 1.3.1 Inbound traffic to the CDE is restricted.14
💼 PCI DSS v4.0 → 💼 1.3.2 Outbound traffic from the CDE is restricted.14
💼 SOC 2 → 💼 CC6.1-7 Restricts Access to Information Assets1212
💼 SOC 2 → 💼 CC6.6-1 Restricts Access1515
💼 UK Cyber Essentials → 💼 1.2 Prevent access to the administrative interface from the internet3336