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Anomaly Detection

This is an optional add-on to the manual AWS Console setup — complete that guide first. It provisions an AWS-managed Cost Anomaly Detection monitor on the management account, so Infracost can surface AWS-detected cost anomalies alongside your cost data.

Check for an existing monitor first​

AWS allows only one managed SERVICE-dimension, DIMENSIONAL-type Cost Anomaly Detection monitor per account — many accounts already have one (for example, a Default-Services-Monitor created via the Cost Explorer console).

  1. Open Billing and Cost Management > Cost Anomaly Detection.
  2. On the Cost monitors tab, look for a monitor with Monitor type: Dimensional and Monitor dimension: Service.

If one already exists, leave it in place — do not create a second one, it will fail. No further action is needed: Infracost discovers and reads it automatically via the ce:Describe*/ce:Get*/ce:List* permissions already granted in the core setup guide.

note

If you are managing a custom cross-account role instead of following the core setup guide exactly, ensure it has the ce:GetAnomalyMonitors and ce:GetAnomalies permissions.

Step 1: Create the monitor​

If no such monitor exists yet:

  1. Open Billing and Cost Management > Cost Anomaly Detection, go to the Cost monitors tab, and click Create monitor.
  2. Monitor name: InfracostServicesMonitor.
  3. Monitor method: Managed by AWS.
  4. Dimension: AWS services.
  5. Click Next.
  6. AWS requires at least one alert subscription to finish creating the monitor — it isn't skippable. Infracost doesn't use it (it reads anomalies directly via the cross-account role), so keep this minimal:
    • Alert subscription: Create a new subscription.
    • Subscription name: anything, for example infracost-unused.
    • Alerting frequency: Weekly summaries.
    • Alert recipients: your own email address.
    • Threshold: set a high value so it rarely fires.
  7. Click Create monitor.

Removing​

Delete the monitor from Billing and Cost Management > Cost Anomaly Detection, on the Cost monitors tab — only do this if you created it for Infracost and nothing else in your account depends on it. If you used a pre-existing monitor, leave it in place.

Troubleshooting​

Creating the monitor fails with "a monitor of this type already exists"​

See Check for an existing monitor first above — leave the existing monitor in place instead of creating a new one.