The scripture in Job 1:12 tells us that the devil and his minions actually exist but cannot take action until God gives them .
When people are under the influence of the devil, they are often sick or in the danger of getting hurt, but Jesus displaying Gods power over all evil always drives out the spirits.
We as believers have the promise of protection as seen in psalms 91.
Evil spirits can tempt, frighten, or try to mislead, but they cannot overpower those who live in faith, prayer, and obedience to God.
These spirits cannot truimph over believers who live by faith, all they can do is to frighten you, tempt you or try to lead you in the wrong direction.
By the power of God, we as believers are protected, conquerors and secured.