bringing home an undersocialized 1-3 year mutt

Question
i'll be taking home my aunt's dog ("Kekai") who is estimated at being 1.5-2 years old. he was found as a tiny puppy in a box in front of a grocery store. we're not exactly sure of his breed, but he looks like a combination of american bulldog/boxer or a pit mutt. he's a short, stalky little guy and his front toes point in like a bulldog.

kekai is a sweet, loving dog ONLY AFTER he "meets" you with the aid of someone familiar. when approached by any stranger/foreign animal, he gets very timid, nervous, and defensive. he barks and will attempt to charge, but i noticed after spending time with this dog (and a few walks) that he just seems VERYVERY insecure because he tends to hide behind me before he starts barking at said strangers.

my dad watched this dog for a week and i saw him hit this dog on several occacions. i, for one, stopped this nonsensical behavior whenever i witnessed it, but i'm not sure if he suffered any physical abuse from my cousins, who were the original "parents" of Kekai.

this dog is intelligent and loving enough to be able to turn his behavior around and make him socialable, but what can i do to prepare my house and make it more welcoming for this puppy?
what's the first thing to do when correcting a potential aggressive behavior? is 2 years old too late?

Answer
Chizuru,

I would not of classified the dog as aggressive. Fear is sometimes better dealt with facing what make him so fearful.So if he is unsociable then expose him to people and things that you know he is insecure about. Take a long a few treats that you know he will enjoy and have him focus on you and the treat not what is going around him.
My best advise is to enroll him in group obedience class this way you both will get to bond to each other and he will have a chance to be around other dogs and people in a supervised session.
It's never too late to train a dog. So be kind and patient and show him that everything is ok because you will take the role as leader for him so he can relax.

Lorie