Botnets are a major source of e-mail spam. Botnet related devices, including master, command and control (C&C) servers and infected computers, are decentralized on the Internet, which greatly challenges any party to identify botnets and discover specific botnet-related information. Therefore, information sharing becomes a crucial factor to counter e-mail spam sent by a botnet. This Supplement provides a reference model which can be applied to the interactive gateway system for countering spam, in accordance with Recommendation ITU-T X.1243. In this reference model, spam-countering gateways can share botnet-related information with each other. This Supplement mainly focuses on countering e-mail spam sent by a botnet.