The innovative capabilities of 5G technologies, such as software‐defined networking (SDN) and network function virtualization (NFV), open up a variety of possibilities for improved and novel service provisioning. Nevertheless, technologies such as SDN expand the attack surface of the communication infrastructure, thus necessitating the introduction of additional security mechanisms. These major changes affect various domains, such as industrial and healthcare environments, where smart deployments gradually become a reality. Motivated by the above, this article highlights the benefit of leveraging the flexibility of SDN/NFV‐enabled networks to deploy enhanced, reactive networking functions to provide security and performance guarantees, via the use of service function chaining (SFC). To this extent, an implementation of a reactive security framework is presented. The application of such a framework in two use cases is also presented: The first use case is in a wind park, which is a good example of an industrial application relying on a network with strict performance, security, and reliability requirements. The second use case is related to ambient‐assisted living, a domain promising significant improvements in the health and well‐being of elderly populations, but which also comes with intrinsic security, safety, and privacy concerns.