There is no way of knowing if what you are dealing with is Temperament or it's because your pup lacks confidence. More information is needed to truly decide that.
If it is indeed temperament then you must be very careful with socialization while still doing what you can to socialize.
Crowded areas are not a place for a true Fila. As AB said, you can not count on people to stay away. There are always those "all dogs love me" idiots that will reach out to pet your dog even after you have made it clear that he is not friendly or the person that slips up behind you and grabs him from behind. A true Fila is supposed to react to what they believe is a threat on their own. That means that your dog is not going to look to you to help him decide what to do next.
This is not to say they should be untrained, lunging maniacs so they should be socialized in safety and of course obedience trained, however, they are not supposed to like strangers or accept new people and will protect you when THEY feel a person as a threat so you need to mindful of all that. A true Fila will require you to put them up before bringing in visitors and they WILL bite.
Now, whether you have a Fila with a true temperament, I don't know but I would treat him as if he does to be safe.
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