Distributed Denial-of-Service (DDoS) attacks are one of the major causes of concerns for communication service providers. When an attack is highly sophisticated and no countermeasures are available directly, sharing hardware and defense capabilities become a compelling alternative. Future network and service management can base its operations on equally distributed systems to neutralize highly distributed DDoS attacks. A cooperative defense allows for the combination of detection and mitigation capabilities, the reduction of overhead at a single point, and the blockage of malicious traffic near its source. Main challenges impairing the widespread deployment of existing cooperative defense are: (a) high complexity of operation and coordination, (b) need for trusted and secure communications, (c) lack of incentives for service providers to cooperate, and (d) determination on how operations of these systems are affected by different legislation, regions, and countries. The cooperative Blockchain Signaling System (BloSS) defines an effective and alternative solution for security management, especially cooperative defenses, by exploiting Blockchains (BC) and Software-Defined Networks (SDN) for sharing attack information, an exchange of incentives, and tracking of reputation in a fully distributed and automated fashion. Therefore, BloSS was prototyped and evaluated through a global experiment, without the burden to maintain, design, and develop special registries and gossip protocols.