You will get around any dog one way or another if you want to badly enough.
Having a dog is realistically is to reduce the risks of being targeted by opportunists and as a deterrent IE, making would be thieves look for easier pickings.
I've a thirteen month old boerboel bitch, very switched on and vocal as well as looking the part.
Would she step up if required?, I don't know, and if I don't know neither does the guy looking over my fence, and the majority of people won't chance finding out.