The CSMA/CA protocol is well known to handle the channel access to various users in wireless ad hoc networks using IEEE 802.11 technology. This protocol requires nodes to wait for some time before initiating a transmission to avoid collisions. As a result, the greedy behavior of some misbehaving nodes can try to lower their waiting time in order to access the channel earlier and penalize the other nodes. In order to avoid this misbehavior, we propose in this paper a model based on measuring the linear regression of nodes' access time to the channel. We have demonstrated that this model exhibits a linear regression between the different nodes' access time. This result has been also confirmed by simulations. In this model, each deviation from the estimated slope is considered as a source of cheating from a corresponding node. By using this detection model, we were able to detect most of the misbehaving nodes in wireless ad hoc networks without requiring modifications to the IEEE 802.11 MAC protocol.