NFV (Network Functions Virtualization) is one of the latest promising technologies making networks more flexible, controllable, cost-efficient and innovative. NFV is being utilized extensively for providing cutting edge networking solutions, including virtual cyber security functions. Functions virtualized with NFV such as firewall, deep packet inspection, intrusion detection systems etc. can reside as applications in the network architecture. Determining the deployment locations of these functions in the network is an important research challenge due to the necessity of achieving different operational objectives such as minimizing latency, network load, cost or energy consumption etc. while meeting cyber security requirements. Among these objectives, optimizing the energy consumption of a network is of vital importance to reduce operating expenses. In this study, we propose an ILP (Integer Linear Programming) model for placing virtualized cyber security functions in a network with the objective of minimizing server energy consumption. We implement and test our model on two different network topologies. Experimental results show that our model can reduce energy consumption significantly while providing cyber security at the desired level.