Spam-I-am: A Proposal for Spam Control using Distributed Quota Management

Email spam has reached alarming proportions because it costs virtually nothing to send email; even a small number of people responding to a spam message is adequate incentive for a spammer to send as many messages as possible. Since spammers need to send messages at high rates to as many recipients as they can, quotas on email senders could throttle spam. We argue for separating the allocation of quotas, a relatively rare activity, from the enforcement of quotas, a frequent activity that must scale to the billions of messages sent daily. This paper tackles the quota enforcement problem, where the goal is to ensure that no sender can grossly violate its quota. The challenge is to design an enforcement scheme that is scalable, is robust against malicious attackers or participants, and preserves the privacy of communication, in a large, distributed, and untrusted environment. We discuss the design of such a system, Spam-Iam, based on a managed distributed hash table (DHT) interface, showing that it can be used in conjunction with electronic stamps (for quota allocation) to ensure that any non-negligible reuse of stamps will be detected.