Not in a form that you are classifying them. They certainly exist since they are energy, but they are not hunting anyone or trying to scare someone. They are simply there because they choose to stay a little longer on Earth. Usually, Souls that experienced sudden death in human body want to stay a little longer since there is a big shock because of the sudden transfer. After death, all the consciousness continue its Journey to the Spiritual world but it is not excluded for the consciousness to stay a little longer on Earth as the energy sometimes want to make sure that her close ones are doing fine after their family member death. Souls can also visit Earth whenever they want, to looks around or just to experienced being an energy before life on Earth. Sometimes Souls before their birth on Earth can visit their future parents to remind them of the great Journey ahead of them and to bond with them even sooner. There are plenty of ways for Souls to come on Earth as they wish, since they have all the awareness and energy to manage with. It is very easy for the Soul as she is, to wander around on many planes. And there is absolutely no need to be scared of those energies since there are no demons or evil ghosts.