Silent Attack Hindering in Drum

Gossip based multicast is a scalable and reliable protocol for dissemination of information within a group of interconnected users. Upon receiving or producing a message the process sends (pushes) it to a small constant subset of processes which is randomly selected out of the group of members. Some implementations of gossip based multicasts poll a small subset of processes for new information, effectively pulling, instead of pushing it. In this manner, each message is eventually delivered to every process, with a high degree of probability [ 1]. An intrusion-tolerant version of a gossip-based multicast algorithm, developed by G. Badishi, I. Keidar and A. Sasson [ 2], employs several schemes in order to minimize the effect of DoS attacks on a member. One possible attack on this protocol is one in which a malicious (or a malfunctioning) process acts normally, but actually does not forward any useful messages, and replies to pull requests with null entries, thus affecting the performance of the protocol. In this project we suggest a failure detector for such a malfunction or attack and a way to overcome it.