[tired&retired]

Peter tells us how to test spirits.

We are also told that discernment of spirits is a gift of the Holy Spirit that is given to some people.

[Telepathic Intruder]

John 4:12
This is how you can recognize the Spirit of God: Every spirit that acknowledges that Jesus Christ has come in the flesh is from God, but every spirit that does not acknowledge Jesus is not from God.

But you have to know Jesus in order to tell. I once talked to a sort of new age "spiritualist", who when I brought up the Bible surprised me by their revulsion to it. That was enough for me. It's not the holy spirit that person is listening to.