To enhance spectrum utilization, cognitive radio technology, combined with cooperative spectrum sensing (CSS), enables sensors to utilize the authorized spectrum of primary users. However, due to the open nature of CSS, malicious sensors (MSs) can easily carry out spectrum sensing data falsification (SSDF) attack, which can severely undermine the performance of CSS. To counteract this, we investigate the cost and benefit tradeoff from a malicious perspective, utilizing generalized hard SSDF attack. We first establish a probabilistic attack model to describe the behavior of MSs. Subsequently, we design and quantify calculate the attack benefit and cost and further mathematically demonstrate the existence of an optimal attack probability. Finally, simulation results demonstrate the relationship between the attack probability and the MSs' benefits, as well as the impact of the attack cost on this relationship.