  Software-Defined Networks have seen an increasing in their deployment because
they offer better network manageability compared to traditional networks.
Despite their immense success and popularity, various security issues in SDN
remain open problems for research. Particularly, the problem of securing the
controllers in distributed environment is still short of any solutions. This
paper proposes a scheme to identify any rogue/malicious controller(s) in a
distributed environment. Our scheme is based on trust and reputation system
which is centrally managed. As such, our scheme identifies any controllers
acting maliciously by comparing the state of installed flows/policies with
policies that should be installed. Controllers rate each other on this basis
and report the results to a central entity, which reports it to the network
administrator.
