\input zb-basic \input zb-ioport \iteman{io-port 06067661} \itemau{Hegazy, Islam; Safavi-Naini, Reihaneh; Williamson, Carey} \itemti{Exploiting routing tree construction in CTP.} \itemso{Jung, Souhwan (ed.) et al., Information security applications. 12th international workshop, WISA 2011, Jeju Island, Korea, August 22--24, 2011. Revised selected papers. Berlin: Springer (ISBN 978-3-642-27889-1/pbk). Lecture Notes in Computer Science 7115, 256-270 (2012).} \itemab Summary: Sensor nodes in a Wireless Sensor Network (WSN) are scattered in an environment to collect data. These nodes are limited in resources and cannot process the collected data or store it for long periods of time. Thus, the sensor nodes rely on routing protocols to relay the collected data wirelessly to a central controller for analysis and storage. However, the routing protocols are not immune against malicious nodes because they sacrifice the security aspect to meet the limited resources of the sensor nodes. In this paper, we demonstrate how a malicious node can exploit the computation of link qualities in the Collection Tree routing Protocol (CTP) to disrupt the construction of routing trees. We propose a lightweight detection system to detect this malicious node. The proposed detection system is implemented and evaluated using the network simulator ns-2. The simulation results show that the detection system provides a robust detection. \itemrv{~} \itemcc{} \itemut{wireless sensor networks; link quality routing protocols; collection tree protocol; intrusion detection} \itemli{doi:10.1007/978-3-642-27890-7\_21} \end