Procedimiento para la implementación del Sistema de Información de

The joint part of this research was intended to prove the risk of Wi-Fi occupancy tracking in households. This field hasn’t been researched much. Unfortunately, the chosen environment featuring a shared Wi-Fi network proved to be too difficult to work with. The first part of the

research was to gather data from participating households and extract the devices belonging to them from the network traces. However, the signal strength and other aspects weren’t enough to make a reliable distinction. This prevented the second and most vital part of the research question to be answered:

Is it possible to reliably track occupancy in a household with passive eavesdropping on its Wi- Fi traffic?

As no reliable distinction between devices that did or did not belong to that household could be made, no real conclusion of this question could be derived. Devices that visually matched the schedule gave reasonably high scores with an overall prediction score of 87.8% (+/- 9.75%) across 25 datasets. The rest of the, in total, 55 datasets were lost due to various problems with hardware, software or because no visually matching devices were found in the data.

Although this joint research didn’t produce the proof wanted to show the potential risk people run, it didn’t influence the individual research into a solution. The individual research focussed on using MAC address randomization and variable transmission power to prevent Wi-Fi occupancy tracking without requiring changes to network protocols.

This part was split into multiple steps, starting with recreating a similar research performed on a public Wi-Fi network trace. By recreating these steps and adding the part on variable transmission power, the results could be compared. Unfortunately, the research paper lacked detail in the descriptions of taken actions requiring some guesswork and comparing the results. This gave some idea of which steps were taken, but not enough for a satisfying conclusion. The system did improve the odds (from a victim’s perspective), but not with comparable figures. As the circumstances differed vastly from the intended ones, normal households, this wasn’t regarded a large problem. The next part was to try and prove the use of the proposed system in a household environment. The simulator created for this showed that the proposed system was unable to prevent occupancy tracking. However, due to time constraints, the simulator wasn’t a complete reflection of realistic households. The amount and types of devices were limited as well as usage scenarios. For a final say, the simulator should be expanded but so far, the outlook is grim.

As a last step, the practical implementation was researched. This was firstly to assess the technical possibilities for such a system. Using gratuitous ARP to enrol new MAC addresses looks to be the best option when user inconvenience is also taken into account. It does require network devices to allow this use, which isn’t well documented. Additionally, it does leave a lot of potential ways to reconnect different MACs of the same device. Variable transmission power proved to be difficult as well. Without protocol changes, no signal strength feedback is available allowing for dropped connections due to too-low power settings. A daemon running on the device and communicating via higher network layers is possible, but still requires both sides to be compatible.

Apart from feasibility, the research also uncovered some problems with these implementations, mainly that the system still leaves a lot of tracking possibilities caused by the network protocol (I.e. sequence numbering), the device (spectral fingerprints) and the user’s activities (traffic patterns). Altogether, MAC randomization with variable transmission power cannot be regarded as a viable solution against Wi-Fi MAC tracking in households. The effect so-far is limited at best. And even if the system is improved, implementation is problematic and there are multiple issues remaining that stand in the way of hiding actual occupancy.

9.1.Future work

Although the proposed system seems broken from the start, some directions could be explored further. The problems that occurred in the shared research part prevented a definitive conclusion into the risk of burglars tracking household occupancy via Wi-Fi signals. As stated in the conclusion of the applicable chapter, this research could be rerun with better circumstances such as:

 Normal household environments without a shared network

 Extra features on the measurement equipment such as a real-time clock and a way to keep tabs on the systems operation

 More efficient distribution and retrieval of the devices

The created household simulator could be expanded to better reflect actual households. This will involve:

 More device types that are commonly seen in households, such as tablets and game consoles  Multiple traces per device type, as network activity will probably vary between brands and

models

 More realistic situations like forgetting a phone, not being connected to a network, visitors connecting to the network and such.

The improved simulator could be used to give a realistic overview of the possibilities of the proposed , but also other solutions.

To complicate a burglar’s attempt to recombine “switched” devices, MAC switching systems could be improved by using multiple active sessions per device to hide actual switches. This would, however, have a lot of impact on devices, networks and applications.

Finally, other ways of preventing occupancy tracking can be researched in general. Although the proposed solution may have panned out to be ineffective, that doesn’t mean other solutions aren’t available.