Smart building using IOT technique is used to maintain home automation in a smart way. In order to improve security in the home, the various sensor is used. In that PIR and MQ-6 sensors plays a major role. The data from various sensors are sent to the Arduino board and get stored in the cloud. In this paper home monitoring system with intrusion, detection technique is used. For data security, wireless sensor network (WSN) playa a major role. To facilitate data encryption, a method namely DES based on efficient key generation mechanism was proposed.