Research & Development

Posted by Libby Miller on , last updated

The Walls have Eyes is an experimental installation developed by BBC R&D for Ian Forrester's Ethical Dilemma Cafe at Mozilla festival 2014 (mozfest), and is a collaboration between Libby Miller, Jasmine Cox and Andrew Nicolaou. Ian and Jasmine have a longer blog post in the works about Mozfest, the ethical dilemma cafe and R&D's involvement as space-wranglers at the event.

For this installation, we wanted to investigate how current tools can be used to track you in physical space using the devices you are carrying and using. We were particularly interested in tracking devices based on their Wifi MAC addresses, because these are tools that are being used for tracking people as they shop. MAC (Media Access Control) addresses are potentially unique identifiers assigned to each network interface in a device.

This is part of wider work within our groups investigating the costs and benefits of personalisation of media, but for Mozfest the main aim was to illustrate the possibilities of the technology in order to provoke discussion.

To do this we created three innocuous-looking picture frames, placed strategically around the cafe. These consisted of cheap frames with postcards mounted in them, and a tiny hole for a camera lens to be mounted on the reverse.

A picture frame with a camera

These frames each house a Raspberry Pi with two Wifi cards, a Pi Camera Module, and a USB battery pack. This is all you need to scan for MAC addresses in the area, take pictures, and send all the data off for processing.

We used another Pi to create a private Wifi network for the others to connect to, and to process the results, matching images and MAC addresses by time and resending the matched results over the network via WebSockets for processing and display.

We had a final Pi just to display the results in a browser on a screen, like this:

Mac addresses (obfuscated)

The part that really provoked discussion - by creating a noisy, very visible result of all this silent activity - was a script that turned images into ascii art and sent them to a dot matrix printer. The continuous paper from the refurbished printer sprawled over the mezzanine floor we were on and down to the ground floor.

printer paper on the line

We took parts and hung them up on a makeshift washing line above the entrance of the festival for all to see. As Ian said "You could say it was like airing dirty laundry/data in public."

printer paper reaching the ground floor

This really gave a sense of the volume of data and gave people souvenirs to take away.

These technologies are used by companies to track us for commercial purposes. The ethical dilemma is one we face every time we go into a space with tracking systems like this: do we enjoy the benefits on our mobile phone and be tracked, not knowing what data is being held by whom or used for what? Or do we give up our phones?

If you visited us and we captured images of you or some of your data, we'd like to thank you for taking part, and assure you that your data was always obfuscated, never left our private network, and was deleted after the event. But how far do we trust organisations to do this?


This work builds on the Radiodan platform and previous technical experiments around device proximity. The code is available here.