Consumer drones are readily available for just a couple of hundred dollars and flown by anyone, with no prior training and without a license. Thus, the problem of drones in restricted airspace has become an increasing concern. Given the large physical area these restricted airspaces cover, simply being able to identify a nearby drone has proven challenging. Recent developments in drone detection technology mean that anyone wanting to secure a perimeter in 2018 will have to take into account the threat from above.