The Fila Brasileiro has an instinctive aggressiveness towards strangers, and it doesn't mind showing it. For this reason, it is not judged on signs of aggressiveness in a dog show, even though some Filas are disqualified for being overly aggressive. It is not friendly with other animals and distinctly dislikes other Fila Brasileiros of the same sex. It is tremendously aggressive towards other small animals, like cats. It will not hesitate to injure or kill another animal.
Though the breed has a natural aggressiveness, this can vary from dog and between genders too. The female Fila Brasileiro tends to be more submissive than the male and can make a better household pet. The dog is considered to be dangerous because of its noted aggression and is banned in the UK. You have to have special permission from the courts to own one there. The aggression in this breed is a subject of much experimentation, with some breeders trying to dampen the hostile nature of the dog.
The dogs can be targeted for kidnapping because of their aggressive tendencies. Dog kidnappers will sell the dog for illegal dog fights. So you want to keep the dog isolated from your neighbors and strangers, not just for their safety but for the dog's safety as well.
If you want a great guard dog, the Fila Brasileiro is completely loyal to its owner. The owner needs to be someone who can take charge of a large dog and demands strict obedience. Putting the dog in obedience class when it is young is one way to handle the aggression in this breed. But you will also need to give it further training to control the aggression, especially if you are using it as a guard dog.
Even though the dog's temperament will vary from dog to dog, you do want to be aware that the breed itself is noted for its aggressive tendencies. You should take care to protect yourself, your loved ones, and your neighbors for any inappropriate behavior on the part of the dog. That is your responsibility as an owner; otherwise, you can incur liabilities simply by owning a large dog like the Fila when you can't control it. This means that you take the proper precautions to build an isolated environment for it with a high fence, and posts that are dug deeply into the earth. The gates should be padlocked and securely shut. There should be notices on your property warning strangers to beware of the dog too. The Fila Brasileiro rightfully intimidates many people and you will need to keep that in mind, should utility people refuse to visit your home and/or your neighbors complain to the animal control officers.