Big data applications running on a big data cluster, creates a set of process on different nodes and exchange data via regular network protocols. The nodes of the cluster may receive some new type of attack or unpredictable internal attack from those applications submitted by client. As the applications are allowed to run on the cluster, it may acquire multiple node resources so that the whole cluster becomes slow or unavailable to other clients. Detection of these new types of attacks is not possible using traditional methods. The cumulative network traffic of the nodes must be analyzed to detect such attacks. This work presents an efficient testbed for internal attack generation, data set creation, and attack detection in the cluster. This work also finds the nodes under attack. A new insider attack named BUSY YARN Attack has been identified and analyzed in this work. The framework can be used to recognize similar insider attacks of type DOS where target node(s) in the cluster is unpredictable.