Why do you assume black magick is bad? Please don't call all black magick satanic, its not. Im a practitioner of black magick and I am not satanic. Now, on to your dillema. Yes black magick can be used to hex or curse someone. Perhaps you could use a sigil. Simply copy one, charge it, and hang it in your room or put it under your pillow. Or release it into the astral by burning it.
For some examples of protective sigils, go to:
Logan D. Paul