This paper deals with the designing and implementation of microcontroller based security system to alert when unauthorized persons try to enter in a home. The first phase of security was implemented using a GSM module to send alert message (SMS). To make the system robust additional layers of security has been incorporated by including security devices such as android based door password, manual keyboard to open the door, PIR motion to detect unauthorized person in the home, rotating ultrasonic sensor by servo motor to active the camera to capture image and RF transceiver to produce voice signal to alert people outside the home. The system's main hardware was designed by Arduino based microcontroller ATmega328. Arduino ISP was used for system designing and Arduino serial monitor is used to test the GSM module. The implemented system was seen to perform well.