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
Console
Follow the Security group rules docs to learn how to add a security group rule that will restrict access to a specific port.
CLI
Run describe-security-groups with a filter to expose security groups that allow access to port 53.
