Unrestricted inbound DNS access

Classification:

compliance

Set up the ec2 integration.

Overview

Description

Reduce the possibility of a breach by checking EC2 security groups for inbound rules that allow unfettered access to TCP and UDP port 53, commonly used during DNS resolution when a request is sent from DNS clients to DNS servers or between DNS servers.

Rationale

Malicious activity, such as distributed denial-of-service (DDoS) attacks, can occur when permitting unfettered DNS access.

Remediation

1. Run describe-security-groups with a filter to expose security groups that allow access to port 53.

   describe-security-groups.sh

   Copy

       aws ec2 revoke-security-group-egress
           --group-id your-group-id
           --ip-permissions '[{"IpProtocol": "tcp", "FromPort": 53, "ToPort": 53, "IpRanges": [{"CidrIp": "192.0.2.0/24"}]}]'