A wireless security system you can install yourself sounds pretty good; a wireless home alarm security system that sends the PIN in the clear - not so much. Unfortunately, this was the finding of Dr. Andrew Zonenberg, senior security consultant at IOActive after testing the SimpliSafe system. Disappointing, to say the least.
It appears SimpliSafe's systems send messages unencrypted in the clear over the air. That means it's trivial to send spoofed sensor readings – such as back-door closed – to fool alarm control boxes into thinking no break-in is happening, and replay PIN codes from keypads to activate or deactivate security systems.
A thief just has to loiter near a home with some radio equipment, pick up the unencrypted PIN messages transmitted from a keypad to the control box, and later replay the messages to deactivate the alarm when the homeowners are out.TheRegister