Module: cloudtrail-cloudwatch-alarms

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.

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

Examples

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

Variables

Required Variables

log_group_name (string) required

The cloudtrail cloudwatch log group name

Optional Variables

additional_endpoint_arns (list(string)) optional

Any alert endpoints, such as autoscaling, or app scaling endpoint arns that will respond to an alert

Default value: [ ]

dashboard_enabled (bool) optional

When true a dashboard that displays the statistics as a line graph will be created in CloudWatch

Default value: true

kms_master_key_id (string) optional

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.

Default value: null

log_group_region (string) optional

The log group region that should be monitored for unauthorised AWS API Access. Current region used if none provided.

Default value: ""

metric_namespace (string) optional

A namespace for grouping all of the metrics together

Default value: "CISBenchmark"

metrics optional

The cloudwatch metrics and corresponding alarm definitions

Type:

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
}))

Default value: { }

sns_policy_enabled (bool) optional

Attach a policy that allows the notifications through to the SNS topic endpoint

Default value: false

sns_topic_arn (string) optional

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

Default value: null

Context Variables

The following variables are defined in the context.tf file of this module and part of the terraform-null-label pattern.

additional_tag_map (map(string)) optional

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.

Required: No

Default value: { }

attributes (list(string)) optional

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.

Required: No

Default value: [ ]

context (any) optional

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.

Required: No

Default value:

{
  "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
}

delimiter (string) optional

Delimiter to be used between ID elements.
Defaults to - (hyphen). Set to "" to use no delimiter at all.

Required: No

Default value: null

descriptor_formats (any) optional

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).

Required: No

Default value: { }

enabled (bool) optional

Set to false to prevent the module from creating any resources
Required: No

Default value: null

environment (string) optional

ID element. Usually used for region e.g. 'uw2', 'us-west-2', OR role 'prod', 'staging', 'dev', 'UAT'
Required: No

Default value: null

id_length_limit (number) optional

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.

Required: No

Default value: null

label_key_case (string) optional

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.

Required: No

Default value: null

label_order (list(string)) optional

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.

Required: No

Default value: null

label_value_case (string) optional

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.

Required: No

Default value: null

labels_as_tags (set(string)) optional

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.

Required: No

Default value:

[
  "default"
]

name (string) optional

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.

Required: No

Default value: null

namespace (string) optional

ID element. Usually an abbreviation of your organization name, e.g. 'eg' or 'cp', to help ensure generated IDs are globally unique
Required: No

Default value: null

regex_replace_chars (string) optional

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.

Required: No

Default value: null

stage (string) optional

ID element. Usually used to indicate role, e.g. 'prod', 'staging', 'source', 'build', 'test', 'deploy', 'release'
Required: No

Default value: null

tags (map(string)) optional

Additional tags (e.g. {'BusinessUnit': 'XYZ'}).
Neither the tag keys nor the tag values will be modified by this module.

Required: No

Default value: { }

tenant (string) optional

ID element (Rarely used, not included by default). A customer identifier, indicating who this instance of a resource is for
Required: No

Default value: null

Outputs

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

Dependencies

Requirements

• terraform, version: >= 1.0
• aws, version: >= 4.0

Providers

• aws, version: >= 4.0

Modules

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

Resources

The following resources are used by this module:

• 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)

Data Sources

The following data sources are used by this module:

• 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)

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.

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!