This is how a demon attack works:
First, there is repetitive threats of such. The person has to be impressionable while the threats are made. The witlesses do make such threats often, implying that the demons have possessed people for listening to rock music or buying second hand items that were supposedly infested with demons. When those threats are repeated enough, you begin to believe them.
Next, you do something "wrong". The "offense" is usually possession of something secondhand or that is slightly off-course. Or, perhaps you are going through some struggle with a problem you have been having. What happens next is that your brain will produce the effects of feeling like demon possession. This is a bicameral response to what you have been programmed to believe. Usually, there is a specific action that is necessary to perform (in the witlesses' case, that action is to find the article that is "possessed" or that is creating the "offense", throw it away, and pray to Jehovah. That is the cue your brain uses to terminate the "demon attack". Once you have done all that, your brain will cease acting like demons.
There is another common cause of "demon attacks". Normal phenomena that are explained by science can, when the person is ignorant, mimic a demon attack. I have heard of orange juice pitchers where the lid popped off by a "demon", which turns out is thermal expansion of the air inside the pitcher. Thermal noises are very common in very cold or very hot weather, and happen when the temperature changes very quickly or the heat comes on. This is sometimes mistaken for demons.
Another phenomenon happens just before you get to sleep. You will begin thinking in a disjointed way, which is perfectly normal. Sometimes you hallucinate at that point. Normally, you just forget about it as you drift to sleep. However, if you are woke up at that point, you will feel like a demon has possessed you. In fact, it was nothing more than a dreamlike state that is perfectly normal when a person just gets to sleep.
Now, religion might have a temporary remedy. For instance, the witlesses tell you that, if you pray to Jehovah and get rid of the offending item, the demon "attack" will cease. Which it will, since it has been programmed to stop when you pray to Jehovah and get rid of the item. However, it is not permanent. Chances are, if you have one demon "attack", you will have others since this Jehovah is an Extortioner. You get rid of one "offending" item, the attacks stop. Some time later, it's another item. Or, perhaps you are not doing enough and the demons are "attacking"; the programmed "solution" is going out more in field circus. They are doing this to milk you. It is done intentionally to extort ever more concessions out of you.
However, the permanent remedy is to learn what those demon "attacks" actually are. The better you are at science (or the more effort you are willing to put into learning what happens when things are heated unevenly), the less of those "demon attacks" you are going to have, and you will realize that most of those spooky noises are in fact normal. And, learning how they program you to have demon "attacks" will help you to prevent them all once and for all. Demons in fact do not attack people, and in fact Satan actually wanted to set mankind free from stagnation that would be caused by always obeying external authority. Demons are supposed to follow Satan, and the Satan that the Watchtower portrays actually wants you to be free from oppressive authority.
Notice that Jesus' message was actually very similar. He was preaching against religious groups that were very similar to the Watchtower Society, and wanted people to think on their own. Satan tried to get people to do their own thinking, too. Once I learned that (it didn't take that long for me to figure it out), I pretty much lost all worry about ever being possessed by demons. Now, in fact, I have many "Satanic" songs in my computer and a Ouija board, without even a thought of being possessed by demons.
However, I would be extremely wary about the Watchtower Society. Any organization that claims to represent the Bible, and then tells you not to research the accuracy of its translation or doctrine using independent sources, or tells you not to study the Bible independently, doesn't deserve your membership. Whether or not you worry about demons, you definitely do have to worry about spending your whole life in a closed system. You will spend all your time going from door to door trying to recruit people. You will be hounded to attend every single meeting (three trips to the hall a week). You will have to give up virtually all entertainment or get hounded. You will have to give up your computer (evil internet). You will have to give up the thought of having your children go to college. You will have to get rid of that cross or statue that you like. There will be no more celebrating Christmas or birthdays (compare Luke 2:10-14). You will not be allowed to have a flag in front of your house, or to vote without getting hounded.
Is that the lifestyle you want?