JRTs are amazing for this too in my experience especially if you want a smaller breed that can be somewhat aggressive if you need them to be. They’re great at staying just out of the distance of most intruders while alerting anyone nearby to their presence. Little fuckers are hard to catch and shut up too if you’re not their owners/masters. They’re also amazing at keeping cats, and rodents off your property. Super intelligent, and loyal too. Be warned though it’s another breed that needs a nice size backyard, and plenty of exercise well into its senior years, and they can live to be 20 with average age being 16.