Explanation:
AWS Config Rules are a great way to help you enforce specific compliance controls and checks across your resources and allows for you to adopt an `ideal’ deployment specification for each of your resource types. Each Rule is simply a Lambda function that when called upon evaluates the resource and carries out some simply logic to determine the compliance result with the rule.
Reference: http://docs.aws.amazon.com/config/latest/developerguide/evaluate-config_develop-rules_nodejs-sample.html