Matthew 8:16 (NIV):
When evening came, many who were demon-possessed were brought to him, and he drove out the spirits with a word and healed all the sick.
28 When he arrived at the other side in the region of the Gadarenes, two demon-possessed men coming from the tombs met him. They were so violent that no one could pass that way.
29“What do you want with us, Son of God?” they shouted. “Have you come here to torture us before the appointed time?”
30Some distance from them a large herd of pigs was feeding.
31The demons begged Jesus, “If you drive us out, send us into the herd of pigs.”
32He said to them, “Go!” So they came out and went into the pigs, and the whole herd rushed down the steep bank into the lake and died in the water.
It seems that when a demon possesses a person, it lives inside the person.
and also some women who had been cured of evil spirits and diseases: Mary (called Magdalene) from whom seven demons had come out;
Was Mary possessed by demons?
As soon as Judas took the bread, Satan entered into him. So Jesus told him, "What you are about to do, do quickly."
Was Judas possessed by Satan?