README.md

May 29, 2025 · View on GitHub

Terraform module for creating alarms for tracking important changes and occurances from cloudtrail.

This module creates a set of filter metrics and alarms based on the security best practices covered in the AWS CIS Foundations Benchmark guide.

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Usage

module "metric_configs" {
  source  = "cloudposse/config/yaml"
  # Cloud Posse recommends pinning every module to a specific version
  # version     = "x.x.x"

  map_config_local_base_path = "./catalog"
  map_config_paths           = "*.yaml"

  context = module.this.context
}

module "cloudtrail_api_alarms" {
  source  = "cloudposse/cloudtrail-cloudwatch-alarms/aws"
  # Cloud Posse recommends pinning every module to a specific version
  # version     = "x.x.x"

  log_group_name = "${aws_cloudwatch_log_group.default.name}"
  metrics = module.metric_configs.map_configs
}

For detailed usage which includes setting up cloudtrail, cloudwatch logs, roles, policies, and the s3 bucket - as well as using this module see the example directory

For aditional CIS rules and controls https://docs.aws.amazon.com/securityhub/latest/userguide/securityhub-cis-controls.html#securityhub-cis-controls-3.8

Important

In Cloud Posse's examples, we avoid pinning modules to specific versions to prevent discrepancies between the documentation and the latest released versions. However, for your own projects, we strongly advise pinning each module to the exact version you're using. This practice ensures the stability of your infrastructure. Additionally, we recommend implementing a systematic approach for updating versions to avoid unexpected changes.

Examples

Here's a complete example of using this terraform-aws-cloudtrail-cloudwatch-alarms module.

Requirements

Name	Version
terraform	>= 1.0
aws	>= 4.0

Providers

Name	Version
aws	>= 4.0

Modules

Name	Source	Version
aws_sns_topic_label	cloudposse/label/null	0.25.0
sns_kms_key	cloudposse/kms-key/aws	0.10.0
sns_kms_key_label	cloudposse/label/null	0.25.0
this	cloudposse/label/null	0.25.0

Resources

Name	Type
aws_cloudwatch_dashboard.combined	resource
aws_cloudwatch_dashboard.individual	resource
aws_cloudwatch_log_metric_filter.default	resource
aws_cloudwatch_metric_alarm.default	resource
aws_sns_topic.default	resource
aws_sns_topic_policy.default	resource
aws_caller_identity.default	data source
aws_iam_policy_document.sns_kms_key_policy	data source
aws_iam_policy_document.sns_topic_policy	data source
aws_region.current	data source

Inputs

Name	Description	Type	Default	Required
additional_endpoint_arns	Any alert endpoints, such as autoscaling, or app scaling endpoint arns that will respond to an alert	`list(string)`	`[]`	no
additional_tag_map	Additional key-value pairs to add to each map in `tags_as_list_of_maps`. Not added to `tags` or `id`. This is for some rare cases where resources want additional configuration of tags and therefore take a list of maps with tag key, value, and additional configuration.	`map(string)`	`{}`	no
attributes	ID element. Additional attributes (e.g. `workers` or `cluster`) to add to `id`, in the order they appear in the list. New attributes are appended to the end of the list. The elements of the list are joined by the `delimiter` and treated as a single ID element.	`list(string)`	`[]`	no
context	Single object for setting entire context at once. See description of individual variables for details. Leave string and numeric variables as `null` to use default value. Individual variable settings (non-null) override settings in context object, except for attributes, tags, and additional_tag_map, which are merged.	`any`	{ "additional_tag_map": {}, "attributes": [], "delimiter": null, "descriptor_formats": {}, "enabled": true, "environment": null, "id_length_limit": null, "label_key_case": null, "label_order": [], "label_value_case": null, "labels_as_tags": [ "unset" ], "name": null, "namespace": null, "regex_replace_chars": null, "stage": null, "tags": {}, "tenant": null }	no
dashboard_enabled	When true a dashboard that displays the statistics as a line graph will be created in CloudWatch	`bool`	`true`	no
delimiter	Delimiter to be used between ID elements. Defaults to `-` (hyphen). Set to `""` to use no delimiter at all.	`string`	`null`	no
descriptor_formats	Describe additional descriptors to be output in the `descriptors` output map. Map of maps. Keys are names of descriptors. Values are maps of the form `{<br/> format = string<br/> labels = list(string)<br/>}` (Type is `any` so the map values can later be enhanced to provide additional options.) `format` is a Terraform format string to be passed to the `format()` function. `labels` is a list of labels, in order, to pass to `format()` function. Label values will be normalized before being passed to `format()` so they will be identical to how they appear in `id`. Default is `{}` (`descriptors` output will be empty).	`any`	`{}`	no
enabled	Set to false to prevent the module from creating any resources	`bool`	`null`	no
environment	ID element. Usually used for region e.g. 'uw2', 'us-west-2', OR role 'prod', 'staging', 'dev', 'UAT'	`string`	`null`	no
id_length_limit	Limit `id` to this many characters (minimum 6). Set to `0` for unlimited length. Set to `null` for keep the existing setting, which defaults to `0`. Does not affect `id_full`.	`number`	`null`	no
kms_master_key_id	The ID or alias of the customer master key (CMK) to use for encrypting the Amazon SNS topic. The CMK must have its resource-based policy allow the service `cloudwatch.amazonaws.com` to perform `kms:Decrypt` and `kms:GenerateDataKey` on it. If this variable is not supplied, a CMK with the sufficient resource-based policy will be created and used when configuring encryption for the SNS topic.	`string`	`null`	no
label_key_case	Controls the letter case of the `tags` keys (label names) for tags generated by this module. Does not affect keys of tags passed in via the `tags` input. Possible values: `lower`, `title`, `upper`. Default value: `title`.	`string`	`null`	no
label_order	The order in which the labels (ID elements) appear in the `id`. Defaults to ["namespace", "environment", "stage", "name", "attributes"]. You can omit any of the 6 labels ("tenant" is the 6th), but at least one must be present.	`list(string)`	`null`	no
label_value_case	Controls the letter case of ID elements (labels) as included in `id`, set as tag values, and output by this module individually. Does not affect values of tags passed in via the `tags` input. Possible values: `lower`, `title`, `upper` and `none` (no transformation). Set this to `title` and set `delimiter` to `""` to yield Pascal Case IDs. Default value: `lower`.	`string`	`null`	no
labels_as_tags	Set of labels (ID elements) to include as tags in the `tags` output. Default is to include all labels. Tags with empty values will not be included in the `tags` output. Set to `[]` to suppress all generated tags. Notes: The value of the `name` tag, if included, will be the `id`, not the `name`. Unlike other `null-label` inputs, the initial setting of `labels_as_tags` cannot be changed in later chained modules. Attempts to change it will be silently ignored.	`set(string)`	[ "default" ]	no
log_group_name	The cloudtrail cloudwatch log group name	`string`	n/a	yes
log_group_region	The log group region that should be monitored for unauthorised AWS API Access. Current region used if none provided.	`string`	`""`	no
metric_namespace	A namespace for grouping all of the metrics together	`string`	`"CISBenchmark"`	no
metrics	The cloudwatch metrics and corresponding alarm definitions	map(object({ metric_name = string filter_pattern = string metric_namespace = string metric_value = string alarm_name = string alarm_comparison_operator = string alarm_evaluation_periods = string alarm_period = string alarm_statistic = string alarm_treat_missing_data = string alarm_threshold = string alarm_description = string }))	`{}`	no
name	ID element. Usually the component or solution name, e.g. 'app' or 'jenkins'. This is the only ID element not also included as a `tag`. The "name" tag is set to the full `id` string. There is no tag with the value of the `name` input.	`string`	`null`	no
namespace	ID element. Usually an abbreviation of your organization name, e.g. 'eg' or 'cp', to help ensure generated IDs are globally unique	`string`	`null`	no
regex_replace_chars	Terraform regular expression (regex) string. Characters matching the regex will be removed from the ID elements. If not set, `"/[^a-zA-Z0-9-]/"` is used to remove all characters other than hyphens, letters and digits.	`string`	`null`	no
sns_policy_enabled	Attach a policy that allows the notifications through to the SNS topic endpoint	`bool`	`false`	no
sns_topic_arn	An SNS topic ARN that has already been created. Its policy must already allow access from CloudWatch Alarms, or set `add_sns_policy` to `true`	`string`	`null`	no
stage	ID element. Usually used to indicate role, e.g. 'prod', 'staging', 'source', 'build', 'test', 'deploy', 'release'	`string`	`null`	no
tags	Additional tags (e.g. `{'BusinessUnit': 'XYZ'}`). Neither the tag keys nor the tag values will be modified by this module.	`map(string)`	`{}`	no
tenant	ID element _(Rarely used, not included by default)_. A customer identifier, indicating who this instance of a resource is for	`string`	`null`	no

Outputs

Name	Description
dashboard_combined	URL to CloudWatch Combined Metric Dashboard
dashboard_individual	URL to CloudWatch Individual Metric Dashboard
sns_topic_arn	The ARN of the SNS topic used

Metrics Tracked

Alarm's Name	Description
`AuthorizationFailureCount`	Alarms when an unauthorized API call is made.
`S3BucketActivityEventCount`	Alarms when an API call is made to S3 to put or delete a Bucket, Bucket Policy or Bucket ACL.
`SecurityGroupEventCount`	Alarms when an API call is made to create, update or delete a Security Group.
`NetworkAclEventCount`	Alarms when an API call is made to create, update or delete a Network ACL.
`GatewayEventCount`	Alarms when an API call is made to create, update or delete a Customer or Internet Gateway.
`VpcEventCount`	Alarms when an API call is made to create, update or delete a VPC, VPC peering connection or VPC connection to classic.
`EC2InstanceEventCount`	Alarms when an API call is made to create, terminate, start, stop or reboot an EC2 instance.
`EC2LargeInstanceEventCount`	Alarms when an API call is made to create, terminate, start, stop or reboot a 4x-large or greater EC2 instance.
`CloudTrailEventCount`	Alarms when an API call is made to create, update or delete a .cloudtrail. trail, or to start or stop logging to a trail.
`ConsoleSignInFailureCount`	Alarms when an unauthenticated API call is made to sign into the console.
`IAMPolicyEventCount`	Alarms when an API call is made to change an IAM policy.
`ConsoleSignInWithoutMfaCount`	Alarms when a user logs into the console without MFA.
`RootAccountUsageCount`	Alarms when a root account usage is detected.
`KMSKeyPendingDeletionErrorCount`	Alarms when a customer created KMS key is pending deletion.
`AWSConfigChangeCount`	Alarms when AWS Config changes.
`RouteTableChangesCount`	Alarms when route table changes are detected.

Dashboard Created

Two CloudWatch Dashboards can be created as well, and will be automatically created by default.

CloudWatch Dashboard

Credits

The alarm metric names, descriptions, and filters from this repository were used.

With many thanks to Anton Babenko for pointing it out and saving us a lot of time scouring reference documents and describing alarms!

Check out these related projects.

terraform-aws-cloudtrail - Terraform module to provision an AWS CloudTrail and an encrypted S3 bucket with versioning to store CloudTrail logs
terraform-aws-cloudtrail-s3-bucket - S3 bucket with built in IAM policy to allow CloudTrail logs
terraform-aws-cloudwatch-logs - Terraform Module to Provide a CloudWatch Logs Endpoint
terraform-aws-cloudwatch-flow-logs - Terraform module for enabling flow logs for vpc and subnets.
terraform-aws-ec2-cloudwatch-sns-alarms - Terraform module that configures CloudWatch SNS alerts for EC2 instances
terraform-aws-ecs-cloudwatch-sns-alarms - Terraform module for creating ECS service level alerts that go to an SNS endpoint
terraform-aws-efs-cloudwatch-sns-alarms - Terraform module that configures CloudWatch SNS alerts for EFS
terrform-aws-elasticache-cloudwatch-sns-alarms - Terraform module that configures CloudWatch SNS alerts for ElastiCache
terraform-aws-lambda-cloudwatch-sns-alarms - Terraform module for creating a set of Lambda alarms and outputting to an endpoint
terraform-aws-rds-cloudwatch-sns-alarms - Terraform module that configures important RDS alerts using CloudWatch and sends them to an SNS topic
terraform-aws-sqs-cloudwatch-sns-alarms - Terraform module for creating alarms for SQS and notifying endpoints

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License

Preamble to the Apache License, Version 2.0

Complete license is available in the LICENSE file.

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or more contributor license agreements.  See the NOTICE file
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regarding copyright ownership.  The ASF licenses this file
to you under the Apache License, Version 2.0 (the
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