The Malevolent Spirit is usually the spirit or soul of an evil person who wanted to harm a person that is weak or wants revenge on the living. Usually they attach themselves to a child, elderly, the sick and injuried because they are easy to manipulate. They will also scare and harm other people that are part of their victim's life.
However, not all Malevolent Spirits were once human. There is at least one that was summoned into our world through an Ouija Board. And another that was trapped inside a dybbuk box.
To get rid of a Malevolent Spirit, usually a person or group has to perform an exorcism in order to drive the evil spirits away, a similar way to get rid of demons. Another way is to get rid of objects that keep them in our world, by destroying Ouija Boards, seals that are hidden under a rug or a floor, and any other objects that seem out of place.