This paper presents an overview of cyber maneuvers and their roles in cyber security. As the cyber war escalates, a strategy that preemptively limits and curtails attacks is required. Such a proactive strategy is called a cyber maneuver and is a refinement of the concept of a moving-target defense, which includes both reactive and proactive network changes. The major advantages of cyber maneuvers relative to other moving-target defenses are described. The use of maneuver keys in making cyber maneuvers much more feasible and affordable is explained. As specific examples, the applications of maneuver keys in encryption algorithms and as spread-spectrum keys are described. The integration of cyber maneuvers into a complete cyber security system with intrusion detection, identification of compromised nodes, and secure rekeying is presented. An example of secure rekeying despite the presence of compromised nodes is described.