Blockchain technologies are helping protect corporations from cyber security attacks. In this project, blockchain is optimized to signal distributed denial of service (DDoS) attacks in a cooperative and distributed network defense. By implementing blockchain and software-defined networking, this project provides a collaborative defense solution to reduce the complexity of existing distributed protocols and architectures for gossiping DDoS attacks. Blockchain simplifies existing approaches with an out-of-the-box distributed infrastructure to broadcast addresses without the need to build specialized registries or other distribution mechanisms/protocols or software-defined networks.