The proliferation of Internet of Things (IoT) devices has led to many applications, including smart homes, smart cities and smart industrial control systems. Attacks like Distributed Denial of Service, event control hijacking, spoofing, event replay and zero day attacks are prevalent in smart environments. Conventional Network Intrusion Detection Systems (NIDSs) are tedious to deploy in the smart environment because of numerous communication architectures, manufacturer policies, technologies, standards and application-specific services. To overcome these challenges, we modeled the operational behavior of IoT network events using timed ACs and proposed a novel hybrid NIDS in this paper. A web server is integrated with IoT devices for remote access, and Constrained Application Protocol is employed in inter- and intra-smart device communication. Experiments are conducted in real time to validate our proposal and achieve 99.17% detection accuracy and 0.01% false positives.