Owing to pervasive computing and advanced technology, assistive devices are deployed within smart environments to provide services dedicated to elderly and disabled users. Beside the big help and usefulness provided by such environments for elderly and disabled users , there is still a high demand to make them both safe and secure. The aim of this chapter is to first give an overview of security requirements for smart environments which have been recently studied to better show the lack of security services for elderly and disabled users. These requirements must be fulfilled for elderly or disabled people among the various smart environments considered (homes, offices, schools, workplaces, hospitals and cars). Considering this challenging task, the aim of our contribution will try to cover safety, security, privacy and trust issues, in order to derive some guidelines for future research work dedicated to both elderly and disabled people