Though spook is sometimes a derogatory term for those of African descent it can also refer to CIA/FBI or any high government organization that has tendancies to track people and spook them out in the process.

In short Black spook clarifies that you are referring to a African American or anyone of African descent as opposed to the term for CIA Spooks
Well I like sugar and I like tea,
But I don't like niggers, no sir-ree
Theres only two things in the world that make me puke
And thats a hog eatin slop and a big black spook!
-Johnny Rebel-
by Tekashn April 16, 2010