Sensor systems are acquiring more fame because of their wide range of applications like process automation, environment (habitat) monitoring, seismic monitoring, and battlefield surveillance. Though they are popular because of their applications, they do come with various challenges like random deployment of nodes, limited energy, computation and memory. Apart from these challenges, the most critical aspect to handle is security. Information is exchanged in Wireless Sensor Networks (WSNs) between the nodes through wireless links in 'air' through electromagnetic waves. This feature attracts the invaders to steal data, disrupt the normal system action by disturbing the data flow and so on. WSNs are prone to attacks at various layers of networks like jamming, denial of service, sinkhole, black hole, wormhole to name a few. Each attack is characterized by its own consequences. Various countermeasures are proposed to defend against these various attacks. Out of these attacks, we pick up wormhole attack at network layer because of its unique nature. Wormhole attack can be launched in the network even if the network is secured with cryptographic techniques. In this paper we address wormhole attack by proposing a RTT centered Wormhole Outbreak discovery. Our proposed system is simple with no extra hardware requirement and no tight clock synchronization.