Föhnseher

Published: Thu 03 January 2013

Modified Analog Television, 2011

Föhnseher rises from the scrap heap of analog TV. Unlike other televisions, Föhnseher captures and displays images downloaded by people on surrounding local wireless networks.

Other people’s phones, laptops and tablet computers all become broadcast stations for this device, replacing the forgotten television towers of old.

Foehnseher

The name föhnseher derives from fernseher, the German word for television, and the föhn, a strange warm wind known to the south of Germany. The words have a very similar pronunciation.

Related project, using radio as metaphor, wifio.

Video

Source Code

There are many ways to wirelessly capture and reconstruct images, as is done in the Föhnseher. All one must do is capture all packets, filter for those with images in them, follow the TCP stream and join the payloads together following the sequence number (SN). Once done, put the correct suffix on the end of the blob.

Example source code for GNU/Linux x86 machines can be downloaded here. This example is a basic modification of the project driftnet and is released under the same terms (GNU GPL). Incidentally it seems more stable than the original.

You will need the latest aircrack-ng suite, a wireless network card able to capture in monitor mode and have isolated a target network (by BSSID) in order on which to start a monitor (and then tun) device. Here is a start script (also in the above tarball) for you to use as a guide:

            #!/bin/sh

            #./start-foehnnet <TARGET BSSID> <CHANNEL>

            #kill a few processes lingering from previous
            sudo pkill dhclient 
            sudo pkill foehnnet 
            sudo pkill airtun-ng

            #take down devices 
            sudo ifconfig at0 down
            sudo ifconfig wlan0 down 
            sudo airmon-ng stop mon0
            sleep 1

            #bring up NIC
            sudo ifconfig wlan0 up

            #set channel
            sudo iwconfig wlan0 channel $2
            sleep 1

            #start monitor device
            sudo airmon-ng start wlan0 $2
            sleep 2

            #start tun device 
            sudo airtun-ng -a $1 mon0 & 
            sleep 5 # should be enough time for the tun device to come up

            #bring up tun device
            sudo ifconfig at0 up

Exhibition History

  • Weise7 Incompatible Laboratorium, Labor Berlin 8 (Curated by Kristoffer Gansing), Haus der Kulturen der Welt, 2012
  • Weise7 Studio Exhibition, Weise7 (group show) Berlin, 2011

Affiliated