Get a guard dog, but what ever you do, don't get any signs suggesting the dog may attack. If you do, you admit liablitiy and people have been known to have their dogs destroyed because of it, or worse... If you get a dog, and it 'randomly attacks' someone who comes into your property, and is has no history of doing it, and it is 'out of character' you can get away with it, most times. All this stems from US cases, which sadly make their way into our society here, thats the way the world is but..

Getting too much security, ie: high fences, camera's etc, suggests you have something to hide... these lowlifes tend to want to find out what that is... If there is a big dog, they usually won't risk it, unless their name is Usain Bolt