Wireless sensor network have become widely used in many civil and military issues. Like all other network, it is exposed to attacks but its simplicity structured (CPU & memory) prevent the traditional defense technic to be applied, so they need a special for defense. Most security researches focus on data righteousness and privacy, in this research we focus on attacks that aimed to the power resources which are referred as Denial Of Sleep attacks (DoS), in this attacks the attacker try to keep the sensor in active phase causing the power source to be drained very quickly so that it is a very dangerous attack. In this research we reviewed the sources of energy Loss in wireless sensor network and classified the attacks that target the power resource, we built a simulation module to analysis the B-MAC protocol response to denial of sleep attacks.