This document describes a GSM based industrial security system that uses sensors and a microcontroller. It uses an IR sensor, touch sensor, LDR sensor and temperature sensor to detect intruders and fires. The ATmega48/88 microcontroller is programmed to sense unauthorized persons and fires. If an intruder is detected or a high temperature is measured, a message is sent via GSM modem to alert concerned mobile numbers. The system provides flexible and effective security for industries, museums, colleges and offices.