In July 2018, drones violated the sky over four correctional centers including Brisbane Correctional Center, Brisbane Women's Correctional Center, Walston Correctional Center and Arthur Gorrie Correctional Center in Queensland, Australia, forcing all four correctional centers have been cordoned off. As a special place, prisons contain various open spaces and always face the potential threat of drone intrusion. Anti-drone systems are increasingly becoming a necessary part of prison operations.