EC2 instance blocks Internet ingress to TCP port 22 (SSH)

# Terraform: Restrict SSH so it's not open to the Internet
resource "aws_security_group" "<example_resource_name>" {
  name   = "<example_resource_name>"
  vpc_id = "<example_resource_id>"

  ingress {
    from_port   = 22
    to_port     = 22
    protocol    = "tcp"
    cidr_blocks = ["10.0.0.0/8"] # Critical: restrict SSH to a specific CIDR, not 0.0.0.0/0
  }
}

# CloudFormation: Restrict SSH so it's not open to the Internet
Resources:
  <example_resource_name>:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Restrict SSH
      VpcId: "<example_resource_id>"
      SecurityGroupIngress:
        - IpProtocol: tcp
          FromPort: 22
          ToPort: 22
          CidrIp: 10.0.0.0/8  # Critical: restrict SSH to a specific CIDR, not 0.0.0.0/0