Virtual Private Networks (VPN) represent, in today?s Internet, one of the most interesting applications. This is due both to their usefulness in corporate network scenarios and to the high revenues they guarantee to network providers. In this paper we propose an innovative approach to VPN implementation, exploiting the capabilities of Active Networks. We present a model aiming at building and dynamically configuring VPNs in a modular way and with a high degree of flexibility. We claim that the proposed approach has substantial advantages over traditional techniques and clearly shows how active technologies may help network engineers realize a number of critical applications for next generation networks.