A spook is a concept introduced by the radically egoist thinker Max Stirner to refer to alien ideas that individuals chase instead of their own selfish desires. Spooks identified by Stirner include God, morality, the nation, the race, private property, society, humanity, or any fixed ideas of the self. Today there are other spooks that Stirner would readily identify, such as sexuality, gender, and western culture.
In as far as these concepts truly serve the self, they are not spooks. If one keeps in mind that society is not an entity up in the sky, but something with real phenomenal reality to the individual, it is legitimate to take up positions with respect to it. Nevertheless, one should keep in mind the necessary abstraction that plays a part in this, and consider it only in as far as the self is found behind the abstraction.