  Security in the Internet of Things (IoT) remains a predominant area of
concern. This survey updates the state of the art covered in previous surveys
and focuses on defending against threats rather than on the threats alone. This
area is less extensively covered by other surveys and warrants particular
attention. A life-cycle approach is adopted, articulated to form a "defence in
depth" strategy against malicious actors compromising an IoT network laterally
within it and from it. This study highlights the challenges of each mitigation
step, emphasises novel perspectives, and reconnects the discussed mitigation
steps to the ground principles they seek to implement.
