This weekend I was having problems with my wireless connection dropping ping packets and being generally unreliable. I decided to switch the channel that it was running on, but first I had to check to see which channel had the least amount of traffic on it.
For this I was going to use Kismet. However, the version that ships with Ubuntu is extremely old (2008/2009) so I grabbed the new one off of kismetwireless.net. I installed the official 64 bit .deb file, and during setup I agreed to use suidroot and entered by username to be added to the kismet group.
After logging out (and rebooting), I was still receiving the following error when running kismet from terminal (as a non root user)
[SERVER] ERROR: IPC child Source 'wlan0' requires root permissions to shut down, but [SERVER] we're not running as root. Something is wrong.
After Googling I found the source was a permission problem, and found the solution in the kismet forums:
sudo chmod u-w /usr/bin/kismet* sudo chmod u+s,o-r /usr/bin/kismet_capture