<p>This study proposes a flexible lightweight security framework for Media IoT (Media Internet of Things) using probabilistic multilateral security model and block chain technique. While IoT (Internet of things) is expected to spread, we focused on the Media IoT which is the area of IoT particularly applied on the media related devices, e.g. visual and audio devices. Such Media IoT is also expected to spread rapidly. To implement flexible lightweight security framework, we propose to introduce two techniques which are probabilistic multilateral security model (PMLSM) and block chain. Using PMLSM, scalable flexible security measure can be possible and using block chain, lightweight distributed and scalable system are possible.</p>