This chapter begins by outlining some common properties of channels, infrastructure, and institutions. It connects and critiques the assumptions and interventions of three influential intellectual traditions: cybernetics (via Claude Shannon), linguistics and anthropology (via Roman Jakobson), and actor-network theory (via Michel Serres). By developing the relation between Serres’s notion of the parasite and Peirce’s notion of thirdness, it theorizes the role of those creatures who live in and off infrastructure: not just enemies, parasites, and noise, but also pirates, trolls, and internet service providers. And by extending Jakobson’s account of duplex categories (shifters, proper names, meta-language, reported speech) from codes to channels, it theorizes four reflexive modes of circulation any network may involve: self-channeling channels, source-dependent channels, signer-directed signers, and channel-directed signers. The conclusion returns to the notion of enclosure, showing the ways that networks are simultaneously a condition for, and a target of, knowledge, power, and profit.