I believe u are a first time dog owner else u shouldn't had such queries in mind.....Now buddy...jst enjoy he's puppyhood dayz....He's barely of 5 months and u want him to turn into a guard dog for u....IMPOSSIBLE!!
According to dogs life-span a 1 yr old dog is of 8 years in human terms....Which means even @ 1 year ur pup wud just have the brain and activities of a 8 year old human baby.....Now tell me u expect him to bark and attack @ 5 months....Thtz FUNNY!!
Moreover jst enjoy out thez dayz coz it wont ever return back....N never ever try to make your dog agressive ....That would b real foolish....Dogs are already too agressive 4 d human society after attaining maturity(not puppyhood)....So plzz try n' socialize him as much as possible.