Announcing AWS Budgets Actions
Starting today, you can define the action you want to take in your account when a budget exceeds its threshold (actual or forecasted amounts). This level of control will allow you to reduce unintentional overspending in your account. You can choose among three action types: Identity and Access Management (IAM) policy, Service Control policy (SCPs), or target running instances (EC2 or RDS). For example, you can choose to apply a custom “Deny EC2 Run Instances” IAM policy to a user, group, or role in your account once your monthly budget for EC2 has been exceeded. With the same budget threshold, you can configure a second action that targets specific EC2 instances within a particular region.
Source:: Amazon AWS