The effect is the same as the Counter-UAV from Call of Duty: Modern Warfare 2 and 3. When in effect, enemies' minimaps will be covered with static. Like the Spy Plane, it can be shot down. They can be distinguished from regular spy planes in the air because they fly counter-clockwise.
The Counter Spy Plane appears in Call of Duty: Black Ops as a 4 killstreak. When called in, it obscures every map an enemy player has with static, although the outline of the map is still view able in the pause menu. This also means that when calling in a killstreak which requires a map (such as a Napalm Strike) the map will also be covered in static making it very hard to accurately place the strike. Similarly, the Counter-Spy Plane has the ability to mask the position or presence of incoming hostile kill-streaks such as Napalm Strike, Rolling Thunder, Mortar, Chopper Gunner and similar items which have a unique icon on the mini-map, making their approach unpredictable. The Counter-Spy Plane also greatly slows down an enemy team, as they have to rely on their eyes and ears purely to locate enemies.