For AI agents: A markdown version of this page is available at https://docs.datadoghq.com/security/code_security/iac_security/iac_rules/terraform-aws-cloudwatch-vpc-changes-alarm-missing.md. A documentation index is available at /llms.txt.

CloudWatch VPC changes alarm missing

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Metadata

Id: terraform-aws-cloudwatch-vpc-changes-alarm-missing

Provider: AWS

Platform: Terraform

Severity: Medium

Category: Observability

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Description

To ensure proper monitoring and alerting of changes to Virtual Private Cloud (VPC) configurations, a log metric filter and corresponding CloudWatch alarm should be configured to detect and notify administrators of events such as CreateVpc, DeleteVpc, or ModifyVpcAttribute. If the metric_name attribute in the aws_cloudwatch_metric_alarm resource does not reference the correct log metric filter (for example, metric_name = "XXXX NOT YOUR FILTER XXXX"), the alarm will not trigger on actual VPC changes, leaving unauthorized or accidental modifications undetected. This misconfiguration undermines security monitoring efforts and increases the risk of undetected changes that could impact network segmentation, access control, or data exposure.

Compliant Code Examples

resource "aws_cloudwatch_log_metric_filter" "CIS_VPC_Changes_Metric_Filter" {
  name           = "CIS-VPCChanges"
  pattern        = "{ ($.eventName = CreateVpc) || ($.eventName = DeleteVpc) || ($.eventName = ModifyVpcAttribute) || ($.eventName = AcceptVpcPeeringConnection) || ($.eventName = CreateVpcPeeringConnection) || ($.eventName = DeleteVpcPeeringConnection) || ($.eventName = RejectVpcPeeringConnection) || ($.eventName = AttachClassicLinkVpc) || ($.eventName = DetachClassicLinkVpc) || ($.eventName = DisableVpcClassicLink) || ($.eventName = EnableVpcClassicLink) }"
  log_group_name = aws_cloudwatch_log_group.CIS_CloudWatch_LogsGroup.name

  metric_transformation {
    name      = "CIS-VPCChanges"
    namespace = "CIS_Metric_Alarm_Namespace"
    value     = "1"
  }
}
resource "aws_cloudwatch_metric_alarm" "CIS_VPC_Changes_CW_Alarm" {
  alarm_name                = "CIS-3.14-VPCChanges"
  comparison_operator       = "GreaterThanOrEqualToThreshold"
  evaluation_periods        = "1"
  metric_name               = aws_cloudwatch_log_metric_filter.CIS_VPC_Changes_Metric_Filter.id
  namespace                 = "CIS_Metric_Alarm_Namespace"
  period                    = "300"
  statistic                 = "Sum"
  threshold                 = "1"
  alarm_description         = "Monitoring changes to VPC will help ensure that all VPC traffic flows through an expected path."
  alarm_actions             = [aws_sns_topic.CIS_Alerts_SNS_Topic.arn]
  insufficient_data_actions = []
}

Non-Compliant Code Examples

resource "aws_cloudwatch_log_metric_filter" "CIS_VPC_Changes_Metric_Filter" {
  name           = "CIS-VPCChanges"
  pattern        = "{ ($.eventName = CreateVpc) || ($.eventName = DeleteVpc) || ($.eventName = ModifyVpcAttribute) || ($.eventName = AcceptVpcPeeringConnection) || ($.eventName = CreateVpcPeeringConnection) || ($.eventName = DeleteVpcPeeringConnection) || ($.eventName = RejectVpcPeeringConnection) || ($.eventName = AttachClassicLinkVpc) || ($.eventName = DetachClassicLinkVpc) || ($.eventName = DisableVpcClassicLink) || ($.eventName = EnableVpcClassicLink) }"
  log_group_name = aws_cloudwatch_log_group.CIS_CloudWatch_LogsGroup.name

  metric_transformation {
    name      = "CIS-VPCChanges"
    namespace = "CIS_Metric_Alarm_Namespace"
    value     = "1"
  }
}
resource "aws_cloudwatch_metric_alarm" "CIS_VPC_Changes_CW_Alarm" {
  alarm_name                = "CIS-3.14-VPCChanges"
  comparison_operator       = "GreaterThanOrEqualToThreshold"
  evaluation_periods        = "1"
  metric_name               = "XXXX NOT YOUR FILTER XXXX"
  namespace                 = "CIS_Metric_Alarm_Namespace"
  period                    = "300"
  statistic                 = "Sum"
  threshold                 = "1"
  alarm_description         = "Monitoring changes to VPC will help ensure that all VPC traffic flows through an expected path."
  alarm_actions             = [aws_sns_topic.CIS_Alerts_SNS_Topic.arn]
  insufficient_data_actions = []
}

resource "aws_cloudwatch_log_metric_filter" "cis_no_mfa_console_signin_metric_filter" {
  name           = "CIS-ConsoleSigninWithoutMFA"
  pattern        = "{ ($.eventName = \"ConsoleLogin\") && ($.additionalEventData.MFAUsed != \"Yes\") }"
  log_group_name = aws_cloudwatch_log_group.CIS_CloudWatch_LogsGroup.name

  metric_transformation {
    name      = "CIS-ConsoleSigninWithoutMFA"
    namespace = "CIS_Metric_Alarm_Namespace"
    value     = "1"
  }
}

resource "aws_cloudwatch_metric_alarm" "cis_no_mfa_console_signin_cw_alarm" {
  alarm_name                = "CIS-3.2-ConsoleSigninWithoutMFA"
  comparison_operator       = "GreaterThanOrEqualToThreshold"
  evaluation_periods        = "1"
  metric_name               = aws_cloudwatch_log_metric_filter.cis_no_mfa_console_signin_metric_filter.id
  namespace                 = "CIS_Metric_Alarm_Namespace"
  period                    = "300"
  statistic                 = "Sum"
  threshold                 = "1"
  alarm_description         = "Monitoring for single-factor console logins will increase visibility into accounts that are not protected by MFA."
  alarm_actions             = [aws_sns_topic.CIS_Alerts_SNS_Topic.arn]
  insufficient_data_actions = []
}

resource "aws_cloudwatch_log_metric_filter" "CIS_VPC_Changes_Metric_Filter" {
  name           = "CIS-VPCChanges"
  pattern        = "{ ($.eventName = CreateVpc) || ($.eventName = ModifyVpcAttribute) || ($.eventName = AcceptVpcPeeringConnection) || ($.eventName = CreateVpcPeeringConnection) || ($.eventName = DeleteVpcPeeringConnection) || ($.eventName = RejectVpcPeeringConnection) || ($.eventName = AttachClassicLinkVpc) || ($.eventName = DetachClassicLinkVpc) || ($.eventName = EnableVpcClassicLink) }"
  log_group_name = aws_cloudwatch_log_group.CIS_CloudWatch_LogsGroup.name

  metric_transformation {
    name      = "CIS-VPCChanges"
    namespace = "CIS_Metric_Alarm_Namespace"
    value     = "1"
  }
}
resource "aws_cloudwatch_metric_alarm" "CIS_VPC_Changes_CW_Alarm" {
  alarm_name                = "CIS-3.14-VPCChanges"
  comparison_operator       = "GreaterThanOrEqualToThreshold"
  evaluation_periods        = "1"
  metric_name               = aws_cloudwatch_log_metric_filter.CIS_VPC_Changes_Metric_Filter.id
  namespace                 = "CIS_Metric_Alarm_Namespace"
  period                    = "300"
  statistic                 = "Sum"
  threshold                 = "1"
  alarm_description         = "Monitoring changes to VPC will help ensure that all VPC traffic flows through an expected path."
  alarm_actions             = [aws_sns_topic.CIS_Alerts_SNS_Topic.arn]
  insufficient_data_actions = []
}