The advancement of technology is challenging for designers of the security systems. When securing a property or different valuable items, it must be kept into account that often criminals are equipped with performant electric or electronic devices, constructed to disable security systems and to remove any trace of their activity. In consequence, reliable and fast responding security systems must be constructed. This paper proposes a design based on two different microcontrollers, both using Real Time Operating Systems, which has an increased capability to resist at attacks from intruders, and to warn the authorities as soon as a unauthorized access was detected in the secured space. This project is characterized by a low-cost implementation and an efficient operation, given that it is fast responding, and it contains two physically separated modules, making its disabling by intruders more difficult.