5G networks are envisioned to support substantially more users than the current 4G does as a direct consequence of the anticipated large diffusion of Machine-2-Machine (M2M) and Internet of Things (IoT) interconnected devices, often with significantly higher committed data rates than general bandwidth currently available into Long Term Evolution (LTE) and broadband networks. The expected large number of 5G subscribers will offer new opportunities to compromise devices and user services, which will allow attackers to trigger much larger and effective cyberattacks. Significant advances in network management automation are therefore needed to manage 5G networks and services in an efficient, scalable, and effective way while protecting users and infrastructures from a wide plethora of advanced security threats. This paper presents a novel self-organized network management approach for 5G mobile networks where autonomic capabilities are tightly combined with Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies so as to provide an effective detection and mitigation of cyber-attacks.