Ghost prevents players from being shown on radar while an enemy Spy Plane is in the air, similarly to how UAV Jammer and Camouflage work.
Ghost's Pro version prevents automated killstreaks, with the exception of Dogs, from attacking the player. In addition, it removes the red box that marks targets for the player-controlled killstreaks such as the Gunship. It also prevents the player from glowing white in the Infrared Scope or in a Camera Spike. As a final effect, the red cross-hair and name do not appear when an enemy aims at a player using Ghost Pro. Aim Assist still targets Ghost Pro users, however.
Contrary to the in-game description of Ghost, neither Ghost nor Ghost Pro will protect the player from an SR-71 Blackbird, Dogs (except on the Wii version), or from the Motion Sensor (Only Hacker Pro will).