Imposing security in MANET is very challenging and hot topic of research science last two decades because of its wide applicability in applications like defense. Number of efforts has been made in this direction. But available security algorithms, methods, models and framework may not completely solve this problem. Motivated from various existing security methods and outlier detection, in this paper novel simple but efficient outlier detection scheme based security algorithm is proposed to protect the Ad hoc on demand distance vector (AODV) reactive routing protocol from Black hole attack in mobile ad hoc environment. Simulation results obtained from network simulator tool evident the simplicity, robustness and effectiveness of the proposed algorithm over the original AODV protocol and existing methods.