Some embodiments of the invention provide a forwarding element that has a data-plane circuit (data plane) that can be configured to implement a DDoS (distributed denial of service) attack detector. The data plane has several stages of configurable data processing circuits, which are typically configured to process data tuples associated with data messages received by the forwarding element in order to forward the data messages within a network. In some embodiments, the configurable data processing circuits of the data plane can also be configured to implement a DDoS attack detector (DDoS detector) in the data plane. In some embodiments, the forwarding element has a control-plane circuit (control plane) that configures the configurable data processing circuits of the data plane, while in other embodiments, a remote controller configures these data processing circuits.