Q:Does the cross work against ghosts?

A: Now, that's an interesting question we have heard many times. First of all let me ask you a question as well:
If the cross and Christianity was the "cure all" for all "spooks" and hauntings then why churches, cemeteries, chapels (and for example Australia's only monastic town, New Norcia with Benedictine monks as residents) have been reported as a common site for paranormal activity . They all display the cross, they all have clergy regularly visiting it or living around, they all a place of deep meditation or prayers for many devoted and well wishing folk.
Without explaining too much about parapsychology when we talk about paranormal we describe a certain type of energy. If everything was as simple as black and white or good and evil life and afterlife would indeed be like a comic book. But it isn't.
Before Christianity there were other religions and there are still a great deal many. That's why researching folklore is so interesting. A long time ago people would be scared of the idea of a round world until they found out it is round after all. Same with religion and belief, presuming that one religion would "fix" all paranormal activities would be underestimating the works of shamans, medicine men, elders etc.
Talking about energies, the rules of "magic" says that whatever you reflect you will attract.
If you are really expecting bad things happening to you then chances are....they will happen.
For a cross to be able to work it has to be used by someone of great faith and an extreme knowledge of what he is dealing with. Also it is that energy that an entity has to recognize in order to cleanse something restless or less friendly. You can make a home or place friendlier by many ways. Chinese use "Feng Shui"
pagans "smudge" or "sweep" away bad energies, Catholics swing the "censers" , Buddhists meditate or chant, Zulus dance it away, Islam uses the cleansing power of fire....the list goes on and on.
So in a nutshell: Make yourself and your loved ones safe and comfortable by feeling well and confident, by showing respect when due and establishing your own boundaries in your life and in your home. If to achieve that a cross helps you then be it. If it's needed get someone who is well trained to deal with the situation.