AWS Amazon EC2 Network ACL

This page shows how to write Terraform for Amazon EC2 Network ACL and write them securely.

aws_default_network_acl (Terraform)

The Network ACL in Amazon EC2 can be configured in Terraform with the resource name aws_default_network_acl. The following sections describe 4 examples of how to use the resource and its parameters.

Example Usage from GitHub
resource "aws_default_network_acl" "default" {
  default_network_acl_id = var.default_network_acl_id_of_default_vpc

  # no rules defined, deny all traffic in this ACL

resource "aws_default_network_acl" "default-acl" {
  default_network_acl_id =

  ingress {
    rule_no = 100
    action = "allow"
resource "aws_default_network_acl" "dev_default" {
  default_network_acl_id =

  ingress {
    protocol   = -1
    rule_no    = 100
resource "aws_default_network_acl" "default" {
  provider               = "aws.given"
  default_network_acl_id = aws_default_vpc.default.default_network_acl_id

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Explanation in Terraform Registry

Provides a resource to manage a VPC's default network ACL. This resource can manage the default network ACL of the default or a non-default VPC.

NOTE: This is an advanced resource with special caveats. Please read this document in its entirety before using this resource. The aws_default_network_acl behaves differently from normal resources. Terraform does not create this resource but instead attempts to "adopt" it into management. Every VPC has a default network ACL that can be managed but not destroyed. When Terraform first adopts the Default Network ACL, it immediately removes all rules in the ACL. It then proceeds to create any rules specified in the configuration. This step is required so that only the rules specified in the configuration are created. This resource treats its inline rules as absolute; only the rules defined inline are created, and any additions/removals external to this resource will result in diffs being shown. For these reasons, this resource is incompatible with the aws_network_acl_rule resource. For more information about Network ACLs, see the AWS Documentation on [Network ACLs][aws-network-acls].

Tips: Best Practices for The Other AWS Amazon EC2 Resources

In addition to the aws_default_vpc, AWS Amazon EC2 has the other resources that should be configured for security reasons. Please check some examples of those resources and precautions.



Ensure to avoid using default VPC

It is better to define the own VPC and use it.



Ensure your network ACL rule blocks unwanted inbound traffic

It is better to block unwanted inbound traffic.



Ensure to use a customer-managed key for EBS volume encryption

It is better to use a customer-managed key for EBS volume encryption. It can be gain more control over the encryption by using customer-managed keys (CMK).



Ensure to avoid storing AWS access keys in user data

It is better to avoid storing AWS access keys in user data. `aws_iam_instance_profile` could be used instead.



Ensure your security group blocks unwanted inbound traffic

It is better to block unwanted inbound traffic.

Review your AWS Amazon EC2 settings

In addition to the above, there are other security points you should be aware of making sure that your .tf files are protected in Shisho Cloud.

CloudFormation Example

CloudFormation code does not have the related resource.

Frequently asked questions

What is AWS Amazon EC2 Network ACL?

AWS Amazon EC2 Network ACL is a resource for Amazon EC2 of Amazon Web Service. Settings can be wrote in Terraform.

Where can I find the example code for the AWS Amazon EC2 Network ACL?

For Terraform, the purpleteam-labs/purpleteam-iac-sut, seemscloud/terraform-aws-elasticsearch-service and asbubam/2dal-infrastructure source code examples are useful. See the Terraform Example section for further details.


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