This document discusses shape-shifting spam and how Hadoop can help fight against it. It describes the challenges of spam filtering at scale given spammers' ability to rapidly change their techniques. It outlines the evolution of anti-spam techniques from manual and rule-based approaches to machine learning models. It then introduces Hadoop and how its distributed processing capabilities allow for more expressive models that can learn from large datasets and quickly update to match spammers' changes. Examples are given of how Hadoop enables standard reporting, ad hoc queries, campaign discovery, and other applications to provide insights into spammer behavior.