XFINITY Security System Flaw Allows Sneak Attacks By Jamming Radio Frequency

The prognosticators promised us lots of smart home vulnerabilities in 2016 and it only took a couple of days for the first disclosure to come out of the woodwork. A researcher with Rapid7 today reported a flaw in Comcast XFINITY's Home Security System that allows attackers to jam the radio frequency the system the system uses without ever triggering an alert to the home owner.

According to Phil Bosco, security consultant for Rapid7, his team found that all it takes to open windows or doors without detection is interrupting the 2.4 GHz radio frequency band used by the base station to communicate with window and door sensors. Rather than alerting the user to a change in state of the security system, the ZigBee-based system continues to report that the sensors are intact, doors are closed, and no motion is detected -- while any movement in the doors remains unmonitored.

This is a huge black spot on the peace of mind that security system users get when out of the house and checking their phone for updates on the protection of their homes. Attackers would be able to slip in and out of a protected building by using one of a couple of simple attack techniques to carry this out, says Tod Beardsley, security research manager for Rapid7.

"There are any number of techniques that could be used to cause interference or deauthentication of the underlying ZigBee-based communications protocol, such as commodity radio jamming equipment and software -based deauthentication attacks on the ZigBee protocol itself," Beardsley wrote in a blog posted today about the research.

His team initially carried out the testing on this system by putting tin foil around a window/door sensor while the system was armed, and then removing the magnet from the sensor to simulate a radio jamming attack.

"Once the magnet is removed from the sensor, the sensor was unwrapped and placed within a few inches from the base station hub that controls the alarm system," Beardsley says. "The system continued to report that it is in armed state. The amount of time it takes for the sensor to reestablish communications with the base station and correctly report is in an open state can range from several minutes to up to three hours."

The last detail is perhaps one of the most disconcerting. The system has no time limit on a communication interruption before it reports a change in state, and even when communication is back up, there's no consistent way for the base station and sensor to sync back up because the system already thinks nothing has changed.

Unfortunately, the flaw currently has "no practical mitigations," according to the researchers. Rapid7 initially disclosed this issue to the vendor in early November and to CERT later that month.