In this paper, we are interested in the validation of opacity where opacity means the impossibility for an attacker to retrieve the value of a secret in a system of interest. Roughly speaking, ensuring opacity provides confidentiality of a secret on the system that must not leak to an attacker. More specifically, we study how we can verify and enforce, at system runtime, several levels of opacity. Besides already considered notions of opacity, we also introduce a new one that provides a stronger level of confidentiality.