Anti-nodes deployed inside a wireless sensor network can frequently generate dummy data packets that make the nodes relaying them deplete their energy. Especially the nodes closer to the sink fail sooner, because they convey more data packets. This causes the sink to be, disconnected from the sensor network. The counter-measures for this type of attacks, namely spam attacks, should consider that the sensor nodes have limited energy, computational power and memory. In this paper, we propose detect and defend against spams (DADS) scheme. In DADS the vicinity of the detected malicious node is notified about the quarantine region, and nodes do not relay unauthenticated messages coming from a node in the quarantine region. Our experiments show that our scheme fits the requirements of the sensor network.