  In the last few years, a countless number of permissioned blockchain
solutions have been proposed, with each one to claim that it revolutionizes the
way of the transaction processing along with the security and privacy
preserving mechanisms that it provides. Hyperledger Fabric is one of the most
popular permissioned blockchain architectures that has made a significant
impact on the market. However, there are only few papers of finding
architectural risks regarding the security and the privacy preserving
mechanisms of Hyperledger Fabric. This paper separates the attack surface of
the blockchain platform into four components, namely, consensus, chaincode,
network and privacy preserving mechanisms, in all of which an attacker (from
inside or outside the network) can exploit the platform's design and gain
access to or misuse the network. In addition, we highlight the appropriate
counter-measures that can be taken in each component to address the
corresponding risks and provide a significantly secure and enhanced privacy
preserving Fabric network. We hope that by bringing this paper into light, we
can aid developers to avoid security flaws and implementations that can be
exploited by attackers but also to motivate further research to harden the
platform's security and the client's privacy.
