Hanuman is the greatest ever devotee of Lord Rama , and because of his devotion , Hanuman has mystical powers and enormous strength.
Hanuman always lived according to Dharma, and He is the son of Lord Vayu, the wind God. So, Hanuman traveled at wind speed.
Hanuman is God Shiva's ansh ( form / child / possessing few qualities of Shiva ), So he is Chiranjeevi ( immortal ).
Hanuman defeated the strongest demon Lankini, the Guardian to the doors of Lanka and He is so powerful , that Hanuman lifted the Sanjeevani hill and brought it to Lanka.
So, ghosts and evil spirits are always afraid of powerful Hanuman.
Whenever we are scared / frightened, our elders have always told us to chant Hanuman name or Hanuman Chalisa.
One line from Hanuman Chalisa ( 40 mantras ).
Bhooth pishaach Nikat nahi aavey, maha veer jab naam sunavai !
This means that evil spirits and ghosts fear to come near anyone who are chanting Hanuman’s name.
