Flooding Attacks against Secure Time-Critical Communications in the Power Grid

Many communication messages in electric substations of the power grid need to be delivered in a very short time (e.g., 3ms according to IEC 61850). However, the delivery delay of such messages is sensitive to flooding attacks that will increase the delay. IEC 62351 specifies that these messages should be signed with digital signatures to provide authentication. The processing of signature generation and verification further increases the delay of message delivery and makes time-critical messages more sensitive to flooding attacks. In this paper, we first experimentally study how flooding attacks affect the delivery delay of time-critical messages protected with popular authentication schemes both in wireless and wired networks. The experimental results show that flooding attacks can easily increase the delay of time-critical communications in wireless networks but not in wired networks. Then we identify a practical intelligent flooding attack where even a small number of flooding packets can significantly increase the delivery delay in a wired network. Finally, we propose a defense scheme to address the intelligent attack and evaluate its effectiveness.