Fog computing is a distributed computing architecture that extends cloud computing capabilities closer to the edge of a network. It places computing, storage, networking, and security functions between IoT devices and centralized cloud servers. This reduces latency, bandwidth consumption, and dependence on distant cloud infrastructure. Fog computing has several important applications in IoT Security because it enables data to be processed and protected near the source. One major application of fog computing is smart home security. IoT devices such as smart cameras, door sensors, motion detectors, and smart locks continuously generate data. Instead of sending all information to the cloud, a nearby fog node can analyze the data locally. Suspicious activities, unauthorized access attempts, or abnormal sensor readings can be detected quickly. This reduces response time and also prevents unnecessary transmission of sensitive household information to external servers. Fog computing is also widely used in smart cities. Smart traffic lights, surveillance cameras, environmental sensors, parking systems, and public safety devices