Active networking is a promising new technology that promises to provide powerful and flexible networking services, with services deployed by packets as they traverse the network. Security for both network operator and user is one of the most challenging aspects in this new network paradigm. This paper describes our experiences in developing security solutions that meet the requirements for three different increasingly complex network environments. Our solutions provide for authorization control, with strong end-end authentication, consideration for the protection of packets that may change in transit, and a flexible policy mechanism that was, in the third prototype, dynamic as well.