Human Security against the risks of burglary, gas Leakage, and fire accident is the main objective of this research. This paper demonstrates the design and Implementation of IoT based security system in buildings via Node MCU and Blynk server with WiFi network connectivity. This system comprises wireless slave sensor nodes and a master controller node. Remote user alerts, portability, configured by the user and power saving and reliability are the main features of our proposed system. WiFi enabled IoT module processes the sensor-based events and transmits the sensor status to the controller. Upon receiving the event notification, the controller alerts the user locally by alarm a siren and remotely via notification, email using Blynk mobile application, phone call and SMS using GSM module. The IoT module makes the node small-size, cost-effective and easy to use. The proposed system is globally monitored and controlled.