Need of wireless communication is increasing to work from distance. That is why new applications are made everyday which increases demand of spectrum but due to limitation of spectrum and inefficient utilization of spectrum. A new paradigm is constituted which is called Cognitive Radio Network (CRN). It get more attention in recent times due to most promising solution for the efficient utilization of spectrum. Spectrum sensing in CRN makes it prone to many attacks on each layer. One of these attacks is PUE attack where a malicious user pretends to be a primary user and not let others to use primary user's channel in its absence. It may cause Denial of Service attack in the network. There are many techniques available in the literature for detection and prevention of PUE attack but still there are some limitations in these approaches. Current research provides detection results based on the energy level of all users in the network. In this paper we provide a novel approach to prevent PUE attacker based on signal activity patterns. Simulation is done in MATLAB-2013 and results show that proposed method gives excellent performance.