Byzantine Paxos
Paxos may also be extended to support arbitrary failures of the participants, including lying, fabrication of messages, collusion with other participants, selective non-participation, etc. These types of failures are called Byzantine failures, after the solution popularized by Lamport.
Byzantine Paxos adds an extra message (Verify) which acts to distribute knowledge and verify the actions of the other processors:
Read more about this topic: Paxos (computer Science)