Abstract—Long-Term Evolution (LTE) is one of the most frequently used wireless communication technology. As every wireless network, LTE is vulnerable to physical layer (PHY) jamming attacks due to the broadcast nature of channels. Since the jammer attacks are getting smarter and energy efficient, they can target a specific region or physical channel instead of entire band. Targeting the physical LTE downlink Synchronization Signals (SS) could be the most dangerous objective. In this paper, we investigate LTE PHY jamming attack against only primary and secondary synchronization signals. Jammer detection is performed by using Neyman-Pearson theorem. Then, a countermeasure method is proposed. Simulation results show that the proposed countermeasure can achieve lower pollution and better correct cell id performances during smart jamming attack against SS.