Freenet is a popular peer to peer anonymous network, with the objective to provide the anonymity of both content publishers and retrievers. Despite more than a decade of active development and deployment and the adoption of well-established cryptographic algorithms in freenet, it remains unanswered how well the anonymity objective of the initial freenet design has been met. In this paper the authors develop a traceback attack on freenet, and show that the originating machine of a content request message in freenet can be identified; that is, the anonymity of a content retriever can be broken, even if a single request message has been issued by the retriever.