Mallet is an intercepting proxy for arbitrary protocols. More accurately, it is a framework for building proxies for arbitrary protocols. Mallet provides the basics required of all proxies: A way to receive the data, a way to send the data, and a user interface to intercept and edit the data. It builds on the Netty project, and as such has access to a large, well-tested suite of protocol implementations that can be used to transform a stream of bytes into useful, high-level protocol objects. This workshop will introduce attendees to Mallet, and show how to construct pipelines of arbitrary complexity, to successfully decode and intercept messages in various protocols, as well as automating modifications of the various messages. A basic familiarity with Java will enhance the delegate's understanding of what they are taught, but is not a requirement.