Efficient analysis of lightweight Sybil attack detection scheme in Mobile Ad hoc Networks Mobile Ad hoc Networks (MANETs) are vulnerable to different kinds of attacks like Sybil attack. In this paper we are aiming to present practical evaluation of efficient method for detecting lightweight Sybil Attack. In Sybil attack, network attacker disturbs the accuracy count by increasing its trust and decreasing others or takes off the identity of few mobile nodes in MANET. This kind of attack results into major information loss and hence misinterpretation in the network, it also minimizes the trustworthiness among mobile nodes, data routing disturbing with aim of dropping them in network etc. There are many methods previously presented by different researchers with aim of mitigating such attacks from MANET with their own advantage and disadvantages. In this research paper, we are introducing the study of efficient method of detecting the lightweight Sybil attack with aim of identifying the new identities of Sybil attackers and without using any additional resources such as trusted third party or any other hardware. The method which we are investigating in this paper is based on use of RSS (Received Signal Strength) to detect Sybil attacker. This method uses the RSS in order to differentiate between the legitimate and Sybil identities. The practical analysis of this work is done usingNetwork Simulator (NS2) by measuring throughput, end to end delay, and packet delivery ratio under different network conditions.