Best most intimidating dogs
Many terriers are excellent alert barkers, although the majority will not follow through with biting.
Herding breeds are also often excellent alert barkers, and quite a few of them will back up the barking with protection of the family or property.
Bringing a guard dog into your home does come with a whole lot of extra responsibility though.
This type of guard dog receives little if any training and interaction.
Guard dogs can be much more sophisticated than that, and dogs with highly specialized training are readily available for purchase.
A guard dog, loosely defined, is one that protects property and family (sometimes called family watch dogs or protection dogs).
There is the quintessential 'junk yard' dog whose only purpose is to scare off would-be intruders.