Pervasive computing and communications are (slowly) enabling local ad-hoc services. Preserving privacy in a pervasive environment is one of the key challenges ahead: How can users define their “communication boundaries”? how can the network avoid wasting resources and eventually collapse under the burden of undesired traffic that will be discarded at the receiver machine? In this paper we propose the adoption of distributed filtering techniques implementing a network-wide firewall whose goal is defining precisely, and under the user control, the boundaries in space, time, information content, and logical addressing of a user communication scope. Initial results based on an implementation integrated with OLSR are presented.