The Semantic Web aims at enabling sophisticated and autonomic machine to machine interactions without human intervention, by providing machines not only with data but also with its meaning (semantics). In the Semantic Web, any two strangers can interact with each other automatically and therefore this assumption does not hold. In this setting, traditional security mechanisms are not suitable anymore. Hence, a semantically enriched process is required in order to regulate an automatic access to sensitive information. Policy-based access control provides sophisticated means in order to support protecting sensitive resources and information disclosure. This paper provides an introduction to policy-based security and privacy protection, by analyzing several existing policy languages. Furthermore, it shows how these languages can be used in a number of Semantic Web scenarios.