Modified analog television tunes into wireless devices

Oliver, 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.

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.



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:


#./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


This piece was made and conceived in 2011, a time where SSL/TLS transport (commonly known to users as the https:// in URLs) was not widely adopted. In a modern-day context this piece would be able to capture and reconstruct very few images. Which is good.