Abstract
In this paper we develop a language of mobile agents called uPLAN for describing the capabilities of active (programmable) networks. We use a formal semantics for uPLAN to demonstrate how capabilities provided for programming the network can affect the potential flows of information between users. In particular, we formalize a concept of security against attacks on secrecy by an ‘outsider’ and show how basic protections are preserved in the presence of programmable network functions.